Yep, absurd.
Expect a dealer to attempt to capitalize on anything they can and give you any excuse to low ball every trade. That's just what they do, vibration or not. They'll give you any excuse they can along with their ridiculous trade in price in an attempt to justify it. Had you traded, they would've turned around and attempted to sell your truck in the 50's.
The typical Chevy dealer would've offered the same or near the same trade in value for either of those two brands under similar circumstances.