Even when companies are honest about how "delete" works, they will use weasel language such as "delete from history" or "delete from inbox" instead of actually doing the thing the user intends.
IMO hard deleting things is generally a bad practice until the user wants to delete their entire account or some other very explicit action is executed.
I expect that the big tech companies have all kinds of cold storage backups and no one is going to actually go spelunking in those archives to physically delete my data when I delete an email. It's more likely that they will delete the keys to decrypt it, but even the keys must be safely stored somewhere, so it's the same problem just with less data.