This is the only case of a null sum for these quantities, where no antiparticles are involved. The sum is also null for 2 particles, where one is the antiparticle of the other, allowing their generation or annihilation, and it is also null for the 4 particles that take part in any weak interaction, like the decay of a neutron into a proton, which involves a u quark, a d antiquark, an electron and an antineutrino, and this is what allows the transmutations between elementary particles that cannot happen just through generation and annihilation of particle-antiparticle pairs.

Thus generation and annihilation of groups of such 8 particles are not forbidden by the known laws. The Big Bang model is based on equal quantities of these 8 particles at the beginning, which is consistent with their simultaneous generation at the origin.

On the other hand, the annihilation of such a group of 8 particles, which would lead to the disappearance of some matter, appears as an extraordinarily improbable event.

For annihilation, all 8 particles would have to come simultaneously at a distance from each other much smaller than the diameter of an atomic nucleus, inside which quarks move at very high speeds, not much less than the speed of light, so they are never close to each other.

The probability of a proton colliding simultaneously with a neutron, with an electron and with a neutrino, while at the same time the 6 quarks composing the nucleons would also be gathering at the same internal spot seems so low that such an event is extremely unlikely to ever have happened in the entire Universe, since its beginning.

The plank time is a limit on a measurement process, not the smallest unit of time.

The Planck mass is just the square root of the quotient of dividing the product between the natural units of angular momentum and velocity, by the Newtonian constant of gravitation.

This Planck mass expresses a constant related to the conversion of the Newtonian constant of gravitation from the conventional system of units to a natural system of units, which is why it appears instead of the classic Newtonian constant inside a much more complex expression that computes the Chandrasekhar limit for black holes.

The Planck mass has absolutely no physical meaning (otherwise than expressing in a different system of units a constant equivalent with the Newtonian constant of gravitation), unlike some other true universal constants, like the so-called constant of fine structure (or constant of Sommerfeld), which is the ratio between the speed of an electron revolving around a nucleus of infinite mass in the state with the lowest total energy, and the speed of light (i.e. that electron speed measured in natural units). The constant of fine structure is a measure of the intensity of the electromagnetic interaction, like the Planck mass or the Newtonian constant of gravitation are measures of the intensity of the gravitational interaction.

The so-called "Planck units" have weird values because they are derived from the Newtonian constant of gravitation, which is extremely small. Planck has proposed them in 1899, immediately after computing for the first time what is now called as Planck's constant.

He realized that Planck's constant provides an additional value that would be suitable for a system of natural fundamental units, but his proposal was a complete failure because he did not understand the requirements for a system of fundamental units. He has started from the proposals made by Maxwell a quarter of century before him, but from 2 alternatives proposed by Maxwell for defining a unit of mass, Planck has chosen the bad alternative, of using the Newtonian constant of gravitation.

Any system of fundamental units where the Newtonian constant of gravitation is chosen by convention, instead of being measured, is impossible to use in practice. The reason is that this constant can be measured only with great uncertainties. Saying by law that it has a certain value does not make the uncertainties disappear, but it moves them into the values of almost all other physical quantities. In the Planck system of units, no absolute value is known with a precision good enough for modern technology. The only accurate values are relative, i.e. the ratios between 2 physical quantities of the same kind.

The Planck system of units is only good for showing how a system of fundamental units MUST NOT be defined.

Because the Planck units of length and time happen by chance to be very small, beyond the range of any experiments that have ever been done in the most powerful accelerators, absolutely nobody knows what can happen if a physical system could be that small, so claims that some particle could be that small and it would collapse in a black hole are more ridiculous than claiming to have seen the Monster of Loch Ness.

The Einsteinian theory of gravitation is based on averaging the distribution of matter, so we can be pretty sure that it cannot be valid in the same form at elementary particle level, where you must deal with instantaneous particle positions, not with their mass averaged over a great region of empty space.

It has become possible to use Planck's constant in a system of fundamental units only much later than 1899, i.e. after 1961, when the quantization of magnetic field was measured experimentally. However, next year, in 1962, an even better method was discovered, by the prediction of the Josephson effect. The Josephson effect would have been sufficient to make the standard kilogram unnecessary, but metrology has been further simplified by the discovery of the von Klitzing effect in 1980. Despite the fact that this would have been possible much earlier, only since 2019 the legal system of fundamental units depends on Planck's constant, but in a good way, not in that proposed by Planck.

However, the computing efficiency could be greatly increased by employing reversible operations whenever possible and there are chances that this will be done in the future, but the efficiency will remain far from infinite.