My speculation on the spectator thing is, and this is assuming that spectators are considered a seperate class at first, is that the bots start in that seperate class and see no stimulus to hit a key which would tell the game that they are ready and spawn them in, as Frikbots assume that they will simply spawn into the match ready to fight unless told otherwise.
Well, if that would dismiss the playmode selection window and the proper option was seleced in doing so. I don't know: Unfortunately, I don't play it.
-Slink