What incredibly enough hasn't been brought up yet, is the distinction between gender preference and genital preference. In heteronormativity they're assumed to be the same, but in reality they're not. This way of thinking also lends itself to the flexibility you're describing; note the word "preference".
Flip
So nice hearing that from someone else, I went through that exactly.
Paywalled, but even the bit I could read I don't agree with. It works great where I live, and totally does cut down on lines! The supermarkets I go to usually have one manned line, and 6-8 self-checkout terminals manned by a single employee. In one discount store the person manning the normal line also has the self-checkout, unless someone else is nearby, and that isn't ideal. But even then, I get to stroll past people who can't figure the system out, and maniacs who are either paying with coins or arguing over lettuce prices.
It works fine 80-90% of the time, and the employees are pretty swift to help, because it's usually one of two problems: Either I'm buying alcohol, or fruit and veg that's in season doesn't have uniform weight. Otherwise it works great.
The one grocery store I regularly visit that doesn't have it is a nuisance, because I wait in line every time.
Can't believe they lumped the Scandi countries into "other". Denmark uses "Vuf" ( pronounced almost scarcely like woof) and "vov" about equally, and Sweden + Norway might too.