I was at uni in the US in the early '90s. The default for housing was mixed sex dorms (but single-sex rooms), with very specific and protected single-sex carve-outs.
In reality - the mixed-sex dorms had at one point been "co-ed by floor" - all women on one floor, all men on another. By the '90s, the floors were mixed, but the Housing Office still allocated space by sex - men on one end of the hallway, women on the other. At my school, the hallway "sections" were typically marked with (non-locking) swinging doors - installed mainly to meet modern fire codes. So the closest "bathroom" to anyone's dorm room would normally be shared by people of the same sex.
My freshman year (year 1/4), in a mixed-sex dorm: my neighbour's roommate dropped out and eventually her boyfriend moved in. (The Housing Office allowed mixed-sex room assignments as long as it was by request/consent of all roommates - they just would not assign strangers to a mixed-sex room). He may very well have used the closest lav for a quick wee, but he also schlepped his stuff down the hallway to the de facto "men's" to take a shower. This was the pattern, as far as I remember, with any men around - somebody's boyfriend staying overnight, someone's brother visiting for the weekend, etc. This wasn't spelled out - men weren't banned from the "women's" facilities, or vice versa - it was just normal non-creepy behaviour/good manners. There certainly was the opportunity to creep, but there was also no hesitation about loudly calling out (or even reporting) questionable behaviour. A very new fresh(wo)man might have gone through the motions to placate a creepy dude chatting to her through the shower curtain (and yes, they were/are literally curtains) as Olivia describes - but as soon as she mentioned what had happened, she'd have received clear and unambiguous support and advice to call it out and shut it down next time.
There were single-sex accomodations on campus - one dorm was still "co-ed by floor" and another dorm was all women. There were also group (4 or 5 person) flats available on campus - but much in demand, so usually people couldn't access these until at least their junior (3/4) year; you'd go in as a group to request a flat. I lived in one of these flats for my last two years. At the end of my junior year, two of my housemates graduated, so the remaining three of us were looking for two new people so we could keep the same space. One flatmate, R, was a foreign student (from a South American country) whose strict Roman Catholic parents wouldn't let her live with an unrelated man, so we had to look for only female potential flatmates. It limited our options, but wasn't at all controversial. R said that if she hadn't had the all-women dorm her first two years and the all-women flat her last two, her parents would not have let her go away to university.
Beyond the potential for sexualised violence in mixed sex intimate spaces, which we know is a huge issue - this is what I worry about, specifically (I know there are a great many things to worry about, and not dismissing other concerns):
(1) women being discouraged from recognising and calling out sexualised creepy (and potentially dangerous) behaviour, regardless of the source
(2) women (like R) being denied educational opportunities because they are not allowed to choose/gatekeep boundaries regarding their living space.