The menu is always pared down and simplified during HOS from the spring and summer. It's happened every year for as long as can be remembered. It helps to increase the speed of lines and simplifies food production to keep up with demand.
Maybe it's a case of labor and not product supply being the issue. Of course, then again they usually make huge batches of everything anyways, so I'd guess it's a lack of staff cooking than it is any front-line service employee you actually see.
However, the changes to the sandwich sound like something else because it's not hard to sling a handful of ingredients into a bun and stick chips on the plate to go with: rinse and repeat a billion times.