> That's just wrong. I use android, my partner uses ios. If he creates the passkey in safari, it's not going to get synced over to my phone

It would, if the people implementing it weren't all so obsessed with pushing their own platform-specific solutions over enabling open standards. LastPass works fine on Android, iOS, Mac, and Windows, but each one of those platforms defaults to saving passkeys in their own platform-specific store unless you jump through hoops to specifically save them somewhere else.

But this is well established behaviour in the real world. That the passkey design doesn't take this into account only proves even more that it was designed in a vacuum.