The difference is this:
Early editions: Pcs have abilities, NPCs and Monsters have abilities. The twain might meet, but there's no info to help the DM make them do so... consequently most DMs said no.
3e: Thats BS we need monsters to not do stuff PCs can't do... So monsters should be built with abilities PCs can get... But that takes a lot of time and makes it harder to make monsters do cool mysterious stuff...
4e: PCs have cool PC stuff, Monsters have cool Monster stuff... if Pcs want to do cool monster stuff, DM's have guidelines for making cool monster stuff into cool PC stuff.
But if you don't care to study the nature of how an orc fires a ray of acid, and instead assume he does it in an orcish way you can still do your own cool stuff and move on.