What specifically was planned? Can you be more specific?
Sounds like his plan was to get the car involved out of town and over to the east coast to hide it
Well, from hearing from former detectives (Try “Police off the cuff” on TY for example), they said that if they got a lead, but not solid proof on the suspect, and learned they would be driving cross country, they could track the car. Having police on their route pull them over for a check would allow the cop, with a body cam to get a visual, verify who was in the car, registration, etc. and just give them a warning, while they still were putting evidence together. Its been done before, so that is they why they suggested it.