MG Comment: hidden makes the field always defined ....

I noticed this comment in frm generated files using MG and reactor.

"hidden makes the field always defined.  if this wasn't here, and you deleted this whole field
            from the control, you'd wind up deleting all child records during a genericCommit..."

I tried it and removed both the hidden field and the form field for one of the child tables, and edited the record through the scaffold generated templates and it did not delete the child record. Doesn't cascade delete have to be enabled for the relationship in the DB for this to actually happen or does  Reactor handle it another way.

Guess I am trying to make sure I understand this comment and how it works.

Dan