But is there a way of making this work with regular bluetooth headphones? AFAIK whey you pair them, the HP will remember the device's physical address, so the random apple devices you may have would have to present the same address to the headphones. Hell, this doesn't work on its own, even between a Linux and Windows install on the same PC. You have to manually move some connection information between the two to get e.g. a mouse working in both.

So if Apple figured a way of bypassing this limitation, it's really not clear to me why that should be considered "bad", even if it's clearly better than what the competition does. It's on the bluetooth standard to do better.

Or is your point that apple should have standardized the protocol they use to make this happen?

I don’t think this is a case of Apple crippling non-Apple headphones but more a case of Bluetooth being pretty limited.

Either way, the user experience is still better than on Windows. Whenever I start up my PC it steals my headphones, even if I’m currently listening on another device (or worse, making a phone call). I’ve searched online and it seems there is no way to switch this off. The only solution seems to be to manually unpair or disable Bluetooth after using it.

But that's how bt heaphones work everywhere, right? I have to go and manually pair them.

But once they're paired, they connect automatically to my iphone, and I can select them easily from a list when e.g making a phone call, though they're usually selected automatically when connected.

BT headphones are certainly less reliable at auto-switching, but that process you're going through isn't the norm for me. I just click on the output menu and select my Sony WH-1000XM4 headphones if I want to use them instead of my airpods. I don't have to pair them every time.