So what's up with Activision-Blizzard demanding your phone number now?

[WoodenPints]

Leynos said:

And pre-paid phones don't work.

Where is this coming from? I've never had a contract phone in my life and I've had my pre-paid phone number on my Acti-Blizzard account for ages and it's not stopped me playing any games including Overwatch 2.