I imagine a lot of differences relate to different regional building practices, stemming from both historic trends but also geographic realities. Especially in older areas (but arguably in newer areas, too) you want to permit a greater range of configurations otherwise you risk people abstaining from fixing or replacing unsafe areas, or avoiding permitting altogether. Notably, 8-1/4" is the maximum height--the change allowed more options but people are perfectly free to continue using more common dimensions.

All that really matters is 7-11: the magic ratio for building your own stairs. Perhaps not the most ideal, but the easiest to remember and also trivial to build from common dimensional lumber[1] :)

On a more serious note, what _truly_ matters is consistency of the steps. Interstep deviations are what cause most injuries. After the first or second step, w'ever the rise/run, the brain has already adapted.

[1] 2x6" boards are actually 1.5x5.5". 5.5+1.5==7 and 5.5*2==11. 7-11 is the traditional American rise/run ratio. I think it's mostly coincidental, though, that 2x6 dimensional lumber adds up the way it does.

Couldn't tell you what the philosophy or justification behind MA's stair riser requirement is.

Have you considered that perhaps the engineers who contributed that change to the MA residential code have done their homework, identified value worth pursuing (whether for safety, building optimization, new material availability, future planning, etc.), and decided it was worth going through what surely isn't a painless ECP process to amend what you've dismissed to be trivial minutae?