Let me clarify a bit as I have more time.
In any interaction with a government actor that can refer me to a law enforcement based on minimal evidence, I take great pains to not provide any information that "can be used against me." If I do not answer they can not say I said it. If they ask me where I am going I will say "Gate X" or "Into the sterile area" or even "to the x-ray machine." I can not say my destination as I do not have certainty of that.
I say "Thanks" only partially to be nice. What I really mean but remains unsaid is "Thanks for having the good sense to accept my NEXUS card without being an ignorant twerp. I appreciate that you did not jerk my chain for some ridiculous reason as other TDC's have done. You have performed your task, simple as it is, effectively and competently. I wish you could tell your comrades how to do the same, but I am now dreaming. So if I can just survive the rest of this gauntlet without losing my cool, you can rest assured that your interaction was the first of many good outcomes that had every potential of going bad, but because you seem to be a decent human being, I can proceed unmolested.