This is all a "mini alibi" after killing Stephany. He goes for the coffee in the white shirt, things got out of hand, he kills her, changes clothes, perhaps showers, now he needs an alibi.
However he is not originally aware of the cameras, so he goes out of his room to pretend to be going into his room perhaps because someone is coming, so he knocks on the door, no answer. Better get the clerk to open the door to let him in.
He had an option at that point to walk into the room while the clerk was there and let the clerk discover the body with him, but I think he saw the camera and decided that wasn't going to work.
I want that coffee trip video.