I really liked that scene, and I’ve seen people think it means something more. I think the same. And, well, I see it this way:
Angus is a cold, ceramic bust marked with all the parts of the brain. The solely purpose of these sort of busts is to be used by others when necessary. It’s just an empty copy of a man made for the use of reason and logic. In tonight’s episode, it was broken, but Holmes was fixing it.
So, I see it as an allegory of himself re-building his life. Sherlock Holmes has been severly times referred to as a machine or a stone-hearted human. However, he is a broken man, and he’s trying real hard to fix that. The empty spaces are yet to be placed, he has to re-find himself too, he has to figure out how to cope with life now. And, maybe, that’s what he needed- a bit of Joan Watson smashing him against reality and his issues. And she’s there to help him up during all the process. And she cares truly, for she even remembered Angus’ name!
And I think that’s what I see.