It's not whataboutism. If the claim is that google's actions with manifest v3 is "abusing its market position to their own benefit", but Apple did the same thing when it didn't stand to benefit from it, then it severely undermines that claim.

Sure, it doesn't rule out google was secretly intending on doing it, only internal memos or whatever can prove that definitively. But at the same time, to immediately conclude that google was "abusing its market position", you would have to be maximally uncharitable to google. That's a sad way to see the world. Take for instance, the flak that google got for banning third party cookies. If this is done by anyone else (eg. Firefox), this would be seen as a good thing. However, cynics have opposed this on the basis that such change would disadvantage third party ad networks more than google, thus google was "abusing its market position to their own benefit" and therefore the change was bad.