That would be a reasonable assumption to make, with one big caveat: reddit originally had no official app, so third-party apps were our only options. If we suppose that people rarely change their habits until they're forced to (a claim that seems almost self-evident to me), then it would be reasonable to suppose that a lot of users would still be using those same 3rd-party apps they started out with. Especially considering the official app was kind of crappy from its inception.
If third-party app users made up a large percentage of users, it might also partly explain why spez is so hellbent on his crusade.
old.reddit.com is still an option, for now at least.
But honestly? I'm going to stick to lemmy as much as I can.