I also don't think the men are likely to be doing it on purpose to upset anyone.
I agree that it's likely a combination of
Not used to shutting the door so not automatic
Point about it being v tricky to get in and shut door with sanitary bin is highly pertinent. + men tend to be bigger than women so potentially will have to squish themselves in even more.
The idea of having single rooms out onto a shared corridor, each with their own sink etc is fine (although men won't want to queue). The idea of having the usual bathroom setup with 3 unisex cubicles is much less fine.
Essentially both the men and the women are inconvenienced by this (unless all the women stop using the work toilets thus freeing them entirely up for the men which is what seems to have happened here. A win for equality and no mistake).