Just some ideas concerning the different angles you could look at this from.
The first and most important, at least in my opinion, is intent. I'm going to assume you didn't dream of these things intentionally. When you do it intentionally, it is no longer a "new" technique and becomes merely another form of incubatio, in my opinion. So there is some question of why we dream of it without trying to, and whether or not we can do it on purpose, and if we can what's the best way to classify it for further understanding.
Another thing worthy of note is the common feature of something you're doing manually. Some elements to consider are that it has to do with the hands (which seems to have an almost mystical quality in dreams), and you could consider a relevance in the mechanical, tactile, and even visual nature of it.
The reason I say this is when I was having sleight of hand dreams, I could see my hands and feel the mechanical actions. However, my focus was barely on the cards, so visually my hands were emphasized. I didn't have a relevant recollection of the tactile sensation of the cards either. Of course this is just an individual experience.
Mafia throws a wrench in things with the above ideas, slightly. Mafia is not a manual task. When I was having mafia dreams, my mind was "actively" considering the game. I'd half expect I spoke of it out loud (and now I wonder if the leads I was considering made it from reality to the dreamspace, or if the dreamspace created them entirely!). The most of any physical activity was maybe the act of reading stuff at the forum (and I've had dreams about MM chat and the forum that weren't mafia related either) but in this case the mental activity was more relevant than the physical activity.
So whether it is mental or physical activity that is emphasized presents another way of looking at this concept, in my opinion.
