Twitter will limit 2FA options. What does this mean for users?

My initial reaction was this was stupid as fuck but I actually don't think it's a bad idea now I've read up on it. 2FA still available for free using other methods such as an authenticator app.

Presumably Twitter have to pay to send the 2FA SMS messages whereas using an authenticator app is both free and arguably more secure. So really they're saying, well you can use the SMS version if you really want to but you have to pay for it, otherwise use the better, free version of 2FA that doesn't cost us anything or you anything.

Actually they are removing the ability to use SMS for 2FA for non-paying accounts. SMS is not a great 2FA method but I'm not sure that removing it completely is the best solution. Then again, Twitter does have other 2FA methods, right?