As mentioned in other comment, not all html which looks like a button is a button. It does in fact take extra work to make everything selectable. On native apps it is even harder because the frameworks do not have selection as built in.
To be clear, I HATE that almost everything isn't selectable. It is one of many reasons why I never use mobile apps. Still, somewhere there has to be a line to ship anything.
I think this is where semantic HTML comes in. Doing other wack or bespoke things is, IMO, not just bad form - it's more work. Just do things the easy way and it'll work.
Not making text selectable is extra work. You have to go out of your way to do that. That's the optimization, not the other way around.
If you just do things the way the web expects you will be shocked how much stuff magically works.
The back button too? Yeah, you don't need logic for that. That should just work right off the rip.