I’ve actually noticed this exact thing with elevators before… I was kind of amazed the beep and light were hooked up completely independently from the actual floor selection logic.
It sort of makes sense that the light in the button would just be hooked directly up to the button contacts. The computer would then be polling the buttons separately and it’s possible to miss a button press… These sorts of buttons shouldn’t need a debounce period since pressing any of them a second time doesn’t do anything. If the buttons were interrupt based, this probably wouldn’t happen.