Why GaN charger is the future of charging?

I kinda feel the author misunderstood or misrepresented why GaN is better for chargers.

(disclaimer, I am amateur electronics engineer, never used GaN transistors)

It is not because the chargers require less parts (directly due to GaN transistor) but rather because they would allow to make the design more efficient for a given topology. Now, there are various SMPS topologies and typically you will chose more complex topology if you require more efficiency than your simple topology offers.

So using GaN transistors allow extending usability of a particular topology into higher power application.

GaN transistors have issues, though. As far as I know GaN are depletion type devices which means, essentially, they are normally ON. That's not exactly what you want in a charger where in case your control circuit failed you would want the main transistor to stay open rather than closed.

I would suspect that this "feature" would require more additional parts just to ensure single failure does not leave the switcher fully on rather than off.