>you’d insist AI companies freely share their source code

Myself I don't see those as being related at all. Keeping something secret is allowed. What is not allowed is something being 'not-secret' yet special. Once you share the source code to the world there would be no closing the barn door.

Trade secrets like source code are a core aspect of IP protection.

What and how you can keep a secret is very much under the term IP, if you want to describe something more specific don’t use terms meant to describe something else. If you’re full on “information wants to be free” then the line doesn’t stop at a companies firewall.