Huh. I worked at Star Tours for a long time. Never cut any locks of wheels unless attached to something. And I am TINY too. Never had an issue with dragging a stroller. Now, they may have called security to cut the lock off that one stroller as an exception, or because the leader didn't know what the actual rule is. But technically, that lock is entirely on the stroller (which CAN still be moved) which is the property of the guests. And I guarantee you those guests got Disney to replace the value of that lock when they came back to find their personal property damaged for no reason other than convenience.