Weird. Maybe I've always been given a Quest that was already setup or rooted. I've never bought one myself. I only ran into this issue recently with a Quest 3. Every Quest 1 and 2 I've used I could enable developer mode and do what I wanted. adb just worked after enabling developer mode.

Yeah the developer mode toggle only shows up if you have the developer flag on your account. Maybe you had it switched on at some point? You also need this to run sidequest for example.

I've always had it too because I already had a developer account with them since the first Rift devkit.