Forgive a naive question, but the way this article is written makes it sound like carrier-provided over the air updates may be forced on your phone even if you are running a custom OS build? Or is that not the case.
If you're running a custom build, it's highly unlikely (read impossible) for a carrier update to be applied over your device. If you are running a rooted carrier build, you may end up with an OTA applied over your build that removes your root access.
Motorola has apparently rolled out silent updates that kill root. This is why they are in the "poor" category.
Well, that's not a true statement. Can you point out what wording implies that? If it really is unclear, we'll change it.
The note "Important: phones may change from one category to another when manufacturers and carriers release updates." refers to obtaining root access on a new phone.
Your quote is exactly the part that confused me. I'm not an android developer, so my perhaps naive reading of that segment meant to me that there are two possibilities:
1. regardless of whether you install a custom boot rom, the lowest-level software running on the phone might be impossible to overwrite, so the carriers still have some basic low-level access to your phone to tell android to lock you out.
2. any such feature is part of the code that is itself replaced when you install a custom rom, so would be defeated and you'd be safe (at least as long as the model you buy does not turn out to have become locked down during the manufacturing batch you end up buying).
It sounds like 1 is just not the case, thankfully.
