For Google (and almost every provider that isn't very specifically targeting the highest levels of security at the expense of usability), the answer to the rhet

For Google (and almost every provider that isn't very specifically targeting the highest levels of security at the expense of usability), the answer to the rhetorical question I posed is "yes", which implies that they can read your mail, without having to target you or anything you have. While (as you correctly pointed out) the fact that you lose access to the data if you lose your passphrase doesn't prove that the data is completely inaccessible without it, the opposite (being able to access the data even if you forget/lose all your secrets/keys) conclusively proves that such access is possible.