How? Can you even sign up in third-party apps? Those third-party app users were already Twitter users before. Maybe you meant they wouldn't remain Twitter users because they can't tolerate the default app experience?
I’d already kicked the habit (or rather replaced one addiction with another and moved to mastodon) after the purge of the journalists, but if I hadn’t this would be the end of twitter for me; the first party stuff is borderline unusable.
I suspect Saint Car has misunderstood how dependent power users are on the third party apps.