The help page has this vague statement saying "Those points lead to higher levels of the program, as well as benefits like early access to Google features and special perks from partners"

Obviously covering their backs because "special perks from partners" could mean anything

When you're "deleting" things from services like Google Drive, it's better to think of what you're doing as "hiding things from yourself". It's unlikely that Google actually deleted that data in a way that prevents them from accessing it.