Starship might also have issues with Mnet because Starship was one of the three/four companies involved with Produce rigging/bribing. So Mnet probably refused to let them participate in any type of survival/exposure show.
The issue with this is that Mnet could potentially block current/future Starship groups/idols from coming on their shows, similar to what happened with SM way back when. Sucks for Starship because they are usually the most popular programs.