It's just in-engine stuff from DOS1 and DOS2. Even if it wasn't what do you think would have been finished in the time spent writing the dip subroutine?
I generally agree that dip feels kind of weird and stuff like throwing enemies and shove need to be reevaluated. I like the idea of shoving or even throwing stuff, but as it is stealth and shove work too well together. It also works way too well in certain areas with certain monsters, like the Hook Horrors.
