Freedom of speech is much more than a legal concept about governments and governed. It's also a guideline on how we should structure an open society going at least back to Ancient Greece.
Parrhesia, freedom of speech in the courts and assemblies(and outside public assemblies)?
No, I'm pretty sure it has always had to do with the governments and the governed. It seems popular these days to conflate the general concept tolerance with freedom of speech.
Tolerance has it's limits though as per the tolerance paradox. Freedom of speech says the government shouldn't draw the line, but society at large absolutely should be allowed to.
EDIT: Outside of specific venues and contexts what you could say in Ancient Athens society was much more rigidly defined and there was much less tolerance for breaking those norms than in the USA today.
So tell me, does Facebook have Freedom of Speech in your view?
The tech companies cannot have it both ways. They want to be publishers, then take the responsibilities and liabilities of publishers.
https://www.breitbart.com/tech/2018/09/05/jack-dorsey-says-t...
(In Facebook's case, at least, I'd say that ever since they moved on from the simple chronological "wall" showing posts as submitted, replacing it with a "timeline" where their algorithms - with plenty of input from "sponsors", etc - decide what you'll see, they have chosen to become a content publisher.)
Fine, in the content publisher role they can decide that certain content, or the speech of certain parties, will not be published through their platform.
But then they must also be held responsible for what they do choose to publish - including liability for harmful content such as libel, false advertising, etc.