You are talking about "users" a lot, I doubt the author actually tried to suggest that this was used in some kind of "product" rather that if a encryption can be spread via tweet it makes no difference how you try to ban it's usage, the bad actors ARE going to be able to encrypt their messages, you are just banning honest citizens usage.

Potential bannable use-case for this "bad crypto" is some criminal organization messaging each other and if they are smart enough to use this they can also come up with good password which makes the banning again completely irrelevant and the kicker is that criminals aren't going to use this "bad crypto" they are going to use something even stronger