I used to run a bar and all of my staff were trained about ask for Angela. We even role played some scenarios just to make sure they were sensible.
Yes the posters were in the gents too, needing help on a date is not exclusively a female thing.
For me asking for Angela is a sign that someone needs a specific kind of assistance, otherwise the conversation is long rather than a couple of words whispered in someone's ear. It's easy to say is Angela working rather than the story of the date not working out. It also signals to people that bar staff will help if they are needed.
We were asked once in the time I was there, a woman on a first tinder date who was really unsettled by the guy. She knew we supported ask Angela so asked one of the bar staff to keep an eye on her and help if she asked us to. She succeeded making her own getaway about an hour later. She came back the next week with flowers for the person who helped her.