We could round on this a thousand times. Would he have still left her there though if he knew his DNA was on her? I keep making that point and it keeps being overlooked as an option.
Does it get rid of the complications though? Cetainly doesn't explain things which the other scenario might. What about the moving bedroom door and window/curtains? If we take GM, MO and KM statements of what they saw, it would tend to indicate someone was in the apartment longer than a quick in-and-out snatch like you are proposing.
At 9ish GM states the door is not where they left it, he puts it back where it should be. Around 9.30 MO says the door is now open again. He mentions the room seems slightly lighter than his kids room indicating it might mean the shutters might have now been moved, but more importantly he suggests the curtains were still drawn closed. (Note: I'm not convinced about the light being from the shutters being open, in GMs statement he says that some of the slats on the shutters were left open anyway). Then when KM does her check at 10, the curtains are now pulled open as is the window.
Now, of course there may be errors or misconceptions occuring in these statements. But on the face of it, it seems to indicate there was activity going on in that apartment from before GM's check (door moved) and until at least after MO's check (curtains still drawn). That's quite a length of time to be in the apartment.