[Newbies] Changing superclass doesn't "work automatically"

I recently came across a piece of behaviour which is (sort of) understandable, but I wonder if it is how it is supposed to happen or not. I was running through the potsdam seaside tutorial, and I change the superclass of one of the objects from Object to WAComponent, and accepted the change. All the browser tools treated the class as if its protocol included the messages of WAComponent, but running code that sent WAComponent messages signaled MessageNotUnderstood.

I fixed the problem by running Compiler recompileAllFrom: 'StMenuComponent'.I cannot reproduce the behaviour in a workspace with subclasses of Object/String.

Any ideas on why this happened, but is not reproduceable in the workspace, and is it supposed to work like that?