I think one thing that has already set it apart is the fact the theme has been announced so far in advance. So compared to a typical jam where you will have to come up with an idea on the spot, here we will have had a chance to think things through. That is unless I have misinterpreted things and there will be an extra theme announced on the actual day layered on top of the slow game thing?
I've taken it as bad form to actually start working on anything in advance, but still having this time to let ideas percolate is qualitatively different to the way things are usually arranged.