I can personally vouch that the judges evaluate even incomplete games. I released one on a previous jam (I didn't have this account at the time)and tried the solo dev route. The 'game' I submitted only had walking, a sprite change, and a single npc pathing route completed by the deadline. They still fully judged what was available of it and gave their thoughts on it.
As for your previous point about people submitting without thought of rewards, I am one of them. I've been following and attempting to take part for a while now and have faith in how it is handled based off personal experience.