The way he slides into Obadiah's lap, when he does, bears little resemblance to the way Tony once did the same on this very couch. It is a matter of practical convenience, a deliberate, unhurried rearrangement of the world into a shape that best supports further kissing. Sherlock does not need physical contact now the way Tony did then. He does not avoid it, either. He just wants this to go on unimpeded, because it is fascinating.