Sherlock is also being very considerate of Ted (in his own way), and has opened his home to him, and helped him with all the stuff with Rupert -- of course Ted is going to be considerate. Especially when it costs him absolutely nothing.

He turns the movie on, then rests comfortably against Joan. It's a very slow and mellow opening, so within the first 10 minutes, the lack of sleep and the various physical exertions seem to catch up with him, and he dozes off, snuggled up against Joan. It helps that Sherlock is there so Ted doesn't feel like he has to be on alert.