The Waterloo and City line may be a little short, but it still needs controlling like any other line. So how is it that the people who do the job are 'mere' signal operators, paid less than they should be and expected to do work that they shouldn't.
It is said that if something waddles like a duck and quacks like a duck, then it is a duck. Well, if someone makes decisions like a controller, answers the phone like a controller, and liaises with station staff and drivers like a controller ... then they are a controller. Except when LUL wants to grade and pay them less, apparently.