Would be more accurate to say un-updated phones are unlocked doors you know are unlocked. Up to date? Slow update cycles measured in weeks suggest for some portion of some number of cycles they're also unlocked.

Worse is how some fraction of updates are very bad news, thus people who care about this delay until there's enough confirmation an update won't do something nasty to something they depend on, which can go all the way to basic phone and SMS usage.