The "don't assume" logic would also apply for feminine sounding names, especially when the name is from a different culture to your own and/or ambiguous. He has the problem of the out of fashion gender neutral he along with guessing incorrectly from name or appearence, but the second issue also applies to she.
Many of us will have been in a professional context (an audio conference call maybe) where someone guessed the person’s gender incorrectly from their name and the sum total of the offence was a shrug, and a quick apology was enough to set things right and move on.
This is a non-issue for almost every person on the planet except for maybe the most easily offended.
It’s about power and dictating what good manners are now and a way to determine quickly if someone is of good breeding and worth continuing with much like how groups used other coded language and gestures in the past.
20 years ago, using they in this way would have really tweaked my ears, but I find myself using it in this way and hearing it in this way more and more, and I think it won't be long before we've forgotten how odd it used to feel.
It still sounds odd to my ears, but that's because I usually hear "they" as a plural pronoun. For example, I was watching a TV show with two siblings, one used "they/them" pronouns. When the mother said "I'm really proud of them and everything they have accomplished", I didn't know if that was referring to one sibling or both.
I know it will probably feel less odd as time goes on.
