While you are correct that it isn't meta to call thermals from hearing footsteps, it depends on the situation. I will now quote Rookieblue: "In very specific circumstances, yes. Have to be in doors, not moving, any allied person not moving, and hear footsteps." -Rookieblue
From what I see, they were walking while Matto was walking as well, which means that any footstep excuses made is pretty much void now. While they have been spoken to by CI command, as stated by Hope, a warning should still be given. +Support