Yeah, kinda true, kinda whataboutism... If calling other people by their chosen pronouns being their biggest problem, is your biggest problem... I'm envious of their life and your life... Thanks, I'm fine, lets not trade lives.
Not OP, but couldn't "what about other, bigger problems?" be construed as whataboutism?
Although personally I'd put it closer to ridicule, which I also believe is John Greene's intent (judging from how he talks about the issue in other social media).
That pronouns isn't a legitimate problem to have, because "what about" more severe problems in life. That Green is implying to trade with the non-issue (or lesser issue) of pronouns.
The problem with your "logic" is that Green never said it was his biggest problem. And if you can find me someone who does say that people not calling others by their correct pronouns is their biggest problem, I would be very surprised.
I would suggest to you that if this was John Green's biggest problem, he wouldn't make a glib tweet about it.
Hmmh. But I mean even that also applies in reverse. Also the "pronouns people" don't say it's their biggest problem. At least the ones I've ever met. So Greens post has the same logical shortcomings as I have.