Here's the Twitter link for the policy change:
https://help.twitter.com/en/rules-an...atforms-policy
I can see trying to increase the friction of people leaving or decreasing people leveraging Twitter to promote their profile somewhere else (though punishing people for this seems odd, I can understand if Zuck came on Twitter saying "hey come to Facebook!", but restricting the users of each platform seems weird other than to try and increase friction for people leaving).
Where it breaks down is what if the actual thing that is being discussed occurred on one of those platforms?
"Did you see what Ye posted on Insta?", except you can't link to it.
"This politician just advocated for death to all dogs on Facebook!", but you can't prove it because a link isn't allowed.