The non-flush gas line connection may serve to assure gas leaks would remain OUTSIDE the wall, to allow odor detection and gas dissipation. By burying the connection behind the wall, potential gas leak would fill your stud bays like a ballon. As a general rule, i wouldn’t stray from original manufacturer’s engineering without calling their tech support.
Are you able to tuck the power cord under the recess so that the oven can flush mount to the wall? I see the outlet is pretty low, but vertical. I was thinking that if the receptacle is side mounted, and low as your is, that the power cord can tuck under that recess.
