Agreed! Knowing the general theme of Slow Games in advance gives us a lot of time to let ideas develop and to assess feasible scope before things get out of control.
(pretty sure there's no secret additional theme, anyway)
You're absolutely on point about giving everyone time to think about their design and I'm interested to see what effect that will have on the games you make. Hopefully it will make for a much more thoughtful and relaxed game jam.
