This is a bad take. By releasing tools like this it helps all websites, including Gmail, have the data on how to speed up their website.
In fact, it wouldn't be hypocritical even if the authors of web.dev themselves worked on a site that did badly.
It is, after all, a tool. It's not a declaration of superior intellect. It's not an article of condescension. It's a tool.
If there's any other decent page speed assistance I'd love to see it.
Wait, was web.dev built by the Gmail team? I always assumed Google was bigger and more complex than that?