You are 1,000% correct. I didn't want to be the messenger delivering unpleasant news, but, this happens every year all over the place. People expect movement after CTE deadlines (because, apparently, they are conditioned to after seeing what happens around PTE deadlines), and are then disappointed when it doesn't happen.
WL spots open up when people with multiple As drop the excess, as happens on 4/30 with PTE deadlines. The same thing simply does not happen at the CTE deadline. What happens is that everyone who is PTE and waiting to be called off someone else's WL is forced to select CTE, and, voila, the class is fully committed. The only time someone doesn't select CTE is if they are holding another A. It happens, but, at this stage of the cycle, it's relatively rare.