I would guess that Reborn just doesn't have waypoints, but perhaps the bot AI for Onslaught is nonfunctional or hasn't been implemented yet at all?
Either way, since both bots and the map Reborn are official and important parts of the game, it seems like this is a bug worth getting some attention in the near future (like before 2.5.2), especially since it may be part of what is holding Nexuiz' Onslaught gametype from becoming popular like CTF is.