Re: How can you transfer anything to Twitter?
"Or worse, phone if you've given your phone number to Facebook (yet another reason I'm glad Facebook doesn't have my phone number)"
Depressingly, you're most likely wrong about this. Although YOU may not have given Facebook your phone number they have most probably siphoned it off your phone if you use any Facebook app, or a device owned by any of your contacts:
https://www.theregister.co.uk/2018/03/25/facebook_app_privacy/