In my opinion, anti-theft features should be always active and your phone should be permanently bound to your account. There should be no way to unlink your phone from within the phone itself. If you want to sell it, you can unlink it from your PC, but there should be no tools for thieves to unblock and unlink the phone.
I live in London. This feature is a must. The amount of theft in recent years is just bonkers.
Does it need to be non-disableable even with the passcode to remain useful?
People really need to learn to think of the details and not the general idea.
In my opinion, anti-theft features should be always active and your phone should be permanently bound to your account. There should be no way to unlink your phone from within the phone itself. If you want to sell it, you can unlink it from your PC, but there should be no tools for thieves to unblock and unlink the phone.