In Windows' File Explorer, F6 cycles focus between window sub-regions, while Alt+D sends you unconditionally to the address bar independent of where the focus is. So maybe there is a parallel here.
Alt-d is, AFAIK, equivalent to a menubar shortcut (like Alt-f) that just happens to go to not quite a menu. None of the others close on repeat, so it doesn't either. UX consistency, though maybe the sort that doesn't matter as much as usual.
That is useful! Wonder why Ctrl-l and alt-d don't work like that?