It's not they do it too, it's "they are the ones who do it". There is no "too" in this context for the average western user. Unless there's proof indicating otherwise.

It's... flips through the list of officially recognized fallacies "tu quoque": https://en.wikipedia.org/wiki/Tu_quoque

"Whataboutism" is trying to deflect to an utterly unrelated topic, like suddenly turning around, pointing at a tree an screaming "but what about the pine needle water content cartel?!".

It certainly isn't pointing out hypocrisy, establishing a common standard or a cureall in online discussions.

I've seen a proper "whataboutism" been used but only once (by a malfunctioning redditor from Eglin Airforce Base).