It’s not a very good back door if you have an explicit easy to use switch to turn it off.

And even without this feature on your device, they don’t need to use a “back door”. They’ll just go through your front door that’s wide open and can’t be closed because of “the children”

If you want to “own” your phone, there are other manufacturers than Apple that allow you to lock it down like Fort Knox (or whatever you deem secure)