I dont think they think things through enough if they want a locking dipstick than why not require a tube and catch can on the vent.
The trans will push fluid out the vent long before it pushes it out the tube.
Then thy might as well say we should have a locking engine oil dip stick as I have seen a lot of those get pushed out and spray oil from problems with crankcase venting.
Again I think they are just to quick to jump and say we need a rule.