That's not true at all. There are many, many cases of people being banned for what I would consider quite mild transphobia. There's was a high profile case this year[0] where a republican Senate candidate was banned for saying,

"Women's sports are for women, not men pretending to be women"

It is not hard to find many more cases and of course the vast majority of banned accounts belong to people with no public profile and you'll never hear about them.

[1] https://www.pbs.org/newshour/politics/twitter-suspends-u-s-s...

From your article:

> Hartzler’s tweet, posted in mid-February, said: “Women’s sports are for women, not men pretending to be women,” _and included her TV ad targeting transgender people in sports and particularly University of Pennsylvania swimmer Lia Thomas._

Emphasis mine.

That’s a fairly mainstream view, and the idea that gender is performance is popular in gender-theory too.