At least here in Washington ST, you need the brakes to be locked up if you move manual lock to full on. Then try to pull forward, your trailer brakes should be locked and holding you in place on a level hard surface. That is one of the field tests you.have to pass if an LEO pulls you over, a d checks to verify your brakes function. IF one or more wheels do.not lock up, you have a failed braking system.
I would suggest anyone reading this, find out what your state, or ones you travel thru require your trailer to do to have a legal setup.
Locking the brakes/wheels while moving is not required. BUT, trailer brakes manually activated need to stop, slow down the whole rig.
OP imho does not have an issue from what I read, generally speaking....Then again.
Marty