"pretending they're not tilting" or not seeing it in their expression or comms, is quite literally you controlling your emotions... which is the antithesis of tilt, so you just proved my point. "Seeing it in their gameplay" isn't tilt either, because that would be an emotional response from an individual. You can still have a positive mindset and learn through a loss, which is what the team has been doing since their inception.
"Tilt in esports is primarily associated with frustration and rage while playing and comes up alongside investigations of toxic or deviant behavior."
If you don't understand what tilt means, well then I don't know what to say.