In an extremely pedantic sense yes I suppose they could, but in practice this is so far on the fringes of things as to be a non-issue.

If you want to get really nitpicky about it you could restrict it to only cases where HSTS headers(of which Google + Chrome really took the lead with) are present.

You could also serve entirely different sites to chrome and to firefox.

I'm sure people try doing this with Googlebot... serving different content to it than to real "users". I wonder if Google tries to detect this by spoofing its user agent sometimes.

I suspect it does, all the time, since it would get gamed frequently with fake filler content.

It's really fascinating all of the problems they must have to juggle in order to make their shit work. :D

Technologically, yes. But a well-behaved site shouldn't do that; it breaks the expectations of both people and tools. Either serve the same content, or (even better) serve a redirect.

I can equally imagine someone being irate if Google treated them the same. Might as well at least be technically correct if you're always going to annoy half of the people either way.