> Why does this matter, unless the only options for 2FA are insecure ones? Secure 2FA today won't depend on your phone number not changing.

The issue is the same with any kind of 2FA software or device.

If you lose, break, or replace your smartphone that has your 2FA app on it, you lose access to everything.

If you don't have a smartphone (likely to be the case for a lot of the people this Twitter thread is talking about), you have to get some kind of OTP generator device/dongle - which can also be lost.