I feel like if/once they reach the number of expected participants (10k), it'd be easy to filter out the spam as long as the majority are truthful.
So what prevents enemy from creating 20knparticipants constantly sending fake data?
Nothing, but what's the value when it's trivial to filter it away based on known good actors? There will be a frontline somewhere, if suddenly it's reporting drones on the other end of the country, and you know there is no good nodes there, you ignore it.