Just because we never see something doesn't mean it isn't there. *G* Do we even know that the infirmary is the *original* Atlantean infirmary or did the expedition just use rooms big enough and close enough to, say, the gateroom? If they turned big rooms that were used otherwise by the Ancients into an infirmary, they could easily have installed earth-like doors to create separate sections, smaller rooms for patients that require quiet etc.

I think what we see and know about the infirmary's layout is less enough that you can make a case for the doors you want without contradicting the canonical setting in a big way.