Cofty you say SBF is trying to say something about our inability to know things not just about how we describe reality. I don't think so because he said this :-
We don't know what it is about how society is currently structured that will be subject to revision. Everything is tentative. That doesn't mean we can't believe in things or hold to certain perspectives we find useful. It just means we should be open to the possibility of revision.
I think he's saying something about our ability to be sure of things. I agree it doesn't seem to be important how we categorise a planet (although it might be if it was a question on 'millionaire' and you hadn't kept up). However if we take his example of mental illness, it certainly mattered to people who were mentally ill if they were treated as evil and chained in dungeon-like conditions or treated as ill and cared for in hospitals.
Changing human knowledge matters, so being dogmatic about what we know now seems inappropriate. This I believe is what this thread is about. If not, I'm sure Slim will tell me.