Playing around with it briefly, it looks like the login is only required to create the room. Our project uses Jitsi for a lot of official meetings, primarily because it's open-source. If it required everyone to log in, that would be more of an issue for us; but as long as the people running the meetings don't mind authenticating with Google, I don't think it will be a problem.

Yeah, I would be much happier if I could create a separate account not linked to any BigCorp. Just let me pick a username and password.

But I guess they are trying to defer some sort of account creation human verification/rate limiting to those companies.

Sure, that means those companies could impersonate users to jit.si, but that would be quite something, so I suspect they wouldn't -- at least for now. So you might trust jit.si with your meetings even though you might not trust Google with your meetings even if you trust Google for authenticating you to jit.si.