historically yes.. that is exactly what they do and is why direct x was used by so many and open gl was left in the stone ages. when initially games came using both, but as dx started doing the work for the devs
"dont crucify me for saying that how i did, it's just easier to say it like that"
it became easier to be lazy and still get the same results. up to a point where what you had actually coded would only work on direct x because you had left out so much open gl dint have a clue what you wanted to do..
this caused a lot of overheads in direct x. And then they decided in dx 12 to fix that... But it seems that devs are used to the extra help from direct x. so they seem to be adding it back in.. Personally i really do hope that this is all they add in.
because there is no point in having dx12 if its no better than dx11. and if its only there to stop mantel/Vulcan being developed for then thats not good for gamers at all..