The problem with reading too much into that comment is that the issue being commented on involves setting up an entire "design process" for ruby, including councils and voting and this and that.

It's troublesome to conflate the bulk of that proposal with the reception of RubySpec itself. It may be that some of the Ruby folks would've been receptive to a more limited proposal like "all released versions of Ruby should pass RubySpec", but we don't live in the universe where that happened.

Even then, telling a group of language developers that they should commit tests into what is effectively your "pet project" is a big ask.