Most service platforms are not public, either, requiring, at minimum, a way to identify the content creator, even if only to the admins. While consuming the content may be anonymous, production is not. The platform itself is only acting as a publisher. In this specific instance, Google is n the wrong.

4chan, being the obvious exception, since content can be created anonymously.

Irrelevant nitpicking. So it's pseudonymous, there is no practical difference.

There’s a huge difference. The government has to let you speak. The corresponding duty on your part is that you won’t do harm (eg., shouting Fire, etC.)

That right, and duty, does not exist on a private platform that you don’t own. You are limited by the TOS and license that you, like most, willfully skip over. A private, non-government platform can tell you to STFU and Get Out and they don’t even need a reason, because it’s their platform.

You can easily set up your own free speech platform, but nobody is required to listen. That’s the main attraction of social media, a more-or-less guaranteed audience. At least until someone tells you to GTFO if you’re not hosting.

You must have replied to the wrong comment.