If the animation were done in pure CSS, UA stylesheets could suppress it handily.

Suggestion to improve the UX for some users by having them write CSS stylesheets? Count me it ;).

Nothing personal, but this sounded a bit surreal to me.

"UA stylesheets" is sort of an intermediary format these days; you don't write them yourself, you use a browser or browser extension or a piece of native accessibility software that generates them for you in response to your described needs.

FWIW iOS has a reduce animation accessibility option. No idea if it's somehow enforced on apps or Google voluntarily respect it in their apps though.