Yeah, I mean you’re absolutely right. There is a male default assumption we tend to have. Maybe it’s a quirk of language, but I think it’s certainly more cultural. Our preconceived notions of “person in internet” is masculine, even though women use the internet just as much and make up half the population. The only time it’s not the case is when you’re in places that are exclusively for women, or in places where the hobby is so dominantly feminine
For simple shit like this, I don’t think it’s particularly harmful or malicious. We invent a person we’re talking to online, and the more often invented person is a man. It’s more a symptom of the greater culture at large, and effectively just a part of our language. We have “they” but I think there’s also a gender-neutral “he” that we just don’t recognize that arose from the male-as-default idea. Intentionally misgendering, on the other hand, is 100% a shitty thing to do, but that’s an argument on a different topic anyway
Almost like that’s what his supporters wanted anyway