Waitlist Game Theory - am I just overthinking?
I don’t think you’re overthinking, you’re just... thinking. But basically, you’re thinking about things that are beyond your control, so in that sense any amount of thinking does not benefit you in any practical sense.
For what it’s worth, many departments hold events allowing admitted students to visit the department (virtually, these days) and meet with faculty. My own department’s event is today and tomorrow, and I had a pleasant meeting with several of the visitors. So I expect many students will be making decisions soon after attending such events. Keep in mind they don’t all know ahead of time their precise order of ranking the different programs (unlike what your intuitive “model” seems to assume), but instead go through a due diligence process where after getting admitted to several schools, they find out more information about each one and then make a decision. There is no reason why this can’t happen well ahead of April 15, and I believe it often does.
Good luck!