With state cops you are allowed to lie under many circumstances (exceptions: identification, under oath, on reports and forms). He could have just straight up

With state cops you are allowed to lie under many circumstances (exceptions: identification, under oath, on reports and forms). He could have just straight up lied, or interpreted the question in a way favorable to him (I thought you meant millions, not less than $100k). He cooperated at all points and was doing nothing wrong. The logical conclusion is that being truthful and cooperative is not going to keep you out of trouble.