Based on the fact that this is affecting name and bio updates, I strongly suspect they're doing this to try and prevent people from finding their Twitter contacts on Mastodon. For those who don't know, there are tools like Fedifinder[0] that will scan your follows/followers' profiles and look for Mastodon URLs so you can follow them there. They're probably trying to make it harder for people to jump ship.

Even if you plan to stay on Twitter, I suggest you try to rebuild your network on Mastodon too if only as a contingency, because it's likely Twitter's now actively trying to prevent people from leaving.

As another commenter mentioned, very reminiscent of the trigger for the Freenode exodus, where the new owner tried to prevent people from talking about their new channels on Libera.

[0] https://fedifinder.glitch.me/