Your syllogism doesn't work. You begin by stating accurately that most companies aren't like Google and Facebook, which is true. Then you implicitly state that Basecamp and Automattic are more representative of most companies, which is patently false in many ways; in the relevant way, it's untrue because most companies do not have remote workers, and most people do not work remotely.

You can't really lead with, "Basecamp and Automattic are closer in size to most companies, and companies of that size employ the most people; therefore they're excellent role models." Size draws a false equivalence, because the remote culture at those two examples depends on far more than size, and they differ from most companies in the same size range.

As for the parent's logic, he is starting from the premise that larger companies have a much stronger signaling effect for business case studies, which in turn prompts changes adopted at other organizations in the same industry regardless of size. I think that's probably a fair premise; it's not necessarily rational, but it's correct that the business practices of large tech companies are reported on, studied and emulated more than smaller companies.