I think of it as more that people wanted to articulate divisions which already existed.
Of course, I was all of four years old in 1970, so...
I was genuinely shocked when I first encountered a separatist TERF in the wild. The feminist lesbians whose work I'd known of B4 that were very kindly, inclusive people. They remembered how they felt being pushed to play-act as straight by hetero feminists, and they weren't having that shit. [sigh]