Maybe - in that case I'm judging them wrongly. But flask (the king they dethroned) was faster to get going (with less features, granted) and their docs feature "Performance" [0] rather prominently.
Note that I don't hold this against them. They simply understand what makes the devs pick them and adjusted their market strategy accordingly. It would be nice if they didn't have to though.
Flask is faster to get going in what way? Writing types instantly saves you a ton of time and effort right out of the gate.[0]
And if your framework is faster, then of course you're going to mention it. Do you really think Flask or Django wouldn't point out that they were fast, if they were? I'm quite sure they would, since it's not shameful to educate the reader on what your framework offers compared to the competition, but they can't, because they're not.
Your link goes to the very bottom of that page, so is it really prominently featured compared to everything else they're trying to sell you on? It really doesn't seem like it. More convincing would be pointing to their list of "key features" at the top, which does mention performance first, but then quickly focuses back on "Fast to code" and "Fewer bugs".
flask took the approach of only providing basic funtionality and relying on 3rd party packages for things like openapi docs and thr like. fastapi has a lot more included and it makes the common tasks like documenting your api easier and more consistent
Note that I don't hold this against them. They simply understand what makes the devs pick them and adjusted their market strategy accordingly. It would be nice if they didn't have to though.
[0] https://fastapi.tiangolo.com/#performance