Probably true. I've heard of cops pulling over drivers because they were "suspiciously" driving under the speed limit. Glad you got out of there ok. Innocent citizens in a free society should not fear the police; sadly this is becoming less the case.
I was a passenger in a car where that exact thing happened.
Someone once posted a police guide to profiling for drug smugglers they had got ahold of. It included driving faster AND driving slower then the posted limit.
Very funny but very sad.