From the article I'd assume this wouldn't work in any way for mobile given no hover, not for screen reader users because a website often has no idea where a screen reader's cursor is, and potentially not for keyboard users (haven't checked if keyboard focus triggers this prefetch/prerender or literally just mouse hover), so ... limited applicability, I'd say.

Part of the design of the feature is that the website doesn't have to specify "on hover" or "on focus", but instead they can just write "eagerness: moderate" (or "conservative", or "eager") and let the browser decide what the exact triggers are. If it turns out that keyboard focus is a useful predictor of whether a link is likely to be clicked, then browsers can add that as a trigger at one of the indicator levels, and websites will automatically get the new behaviour "for free".

Currently, "eagerness: conservative" activates on mouse/pointer down (as opposed to mouse/pointer up, which is when navigation normally happens), which will work for mobile devices as well. And "eagerness: moderate" includes the more conservative triggers, which means that even on devices with no hover functionality, prerendering can still kick in slightly before the navigation occurs.

maybe its the fact that its really easy adding something like this, and this (I think) or something which basically acomplishes the same thing (but in a better way?) are used by some major meta frameworks like nextJS etc.

I guess it has limited applicability but maybe its the small little gains that add victories. I really may be going on in a tangent but I always used to think that hardware is boring / there aren't too many optimizations its all transistors with and,or,not but then.. I read about all the crazy stuff like L1 cache and the marvel machinery that is known as computers. It blew my mind into shredders. Compilers are some madman's work too, the amount of optimization is just bonkers just for tiny performances but those tiny performance boosts in the whole stack makes everything run so fast. Its so cool.