I think this was part of the problem at your lock, there may have been a "shut the gate " sign but it was ignored because there was no obvious reason for it, a case of boy crying wolf, if they had troubled to explain the problem and what they were doing about it it would have been a different story.
There is no reason to shut the gate at Enfield as it is a river section but there was a time when the lock had to be left empty as when full it was flooding the lock house, presumably that is now fixed.
Agree custom on southern GU is to leave gates and of course they self open on the Regents