There is some user benefit to this. There is an old saying that when the attacker has physical access, its game over. But modern products are making that less true. Sure if the government has your device you might still be screwed, but the average person can't do anything with a locked iphone like they could a locked Win 7 era laptop.

It would be fair to have a locked / unmodifiable initial boot step which shows a visible "unsecured" indication on every boot. If you installed a custom OS you can ignore this, if you didn't, you can worry.