But if my partner is just an average guy who’s not raping and killing anyone, then he’s not the reason for the separated spaces so there’s no value getting his opinion on the impact of that changing.
Ignoring the slightly worrying 'if' in that sentence, I'll assume that your partner is in fact a nice guy who doesn't go around raping and killing, SleeplessInWherever. In that case he is the very kind of man women don't have to worry about, because he wouldn't dream of using the women's toilets, because they are the women's toilets, and he being a decent bloke, respects that.
To that extent, although he isn't the reason for separated spaces for women, he is a valued supporter of separated spaces for women because he respects them.
If all men were nice, respectful blokes like your partner, we wouldn't be having a discussion about 'policing' or 'enforcing' women-only spaces. We could just trust men to do what they have done for yonks - stay out of women's toilets.
That's such a simple solution because it makes it easy to spot that a man in the women's toilets is by his very presence not one of those nice respectful men, like your partner is.