We address only the initial stop of each motorist passing through a checkpoint and the associated preliminary questioning and observation by checkpoint officers. Detention of particular motorists for more extensive field sobriety testing may require satisfaction of an individualized suspicion standard.
Excerpts From Supreme Court s Decision Upholding Sobriety Checkpoints - New York Times
and from your case
It took the Court some time to settle on a test for when a "seizure" has occurred, and the Court has recently modified its approach. The issue is of some importance, since it is at this point that Fourth Amendment protections take hold. The Terry Court recognized in dictum that "not all personal intercourse between policemen and citizens involves 'seizures' of persons," and suggested that "[o]nly when the officer, by means of physical force or show of authority, has in some way restrained the liberty of a citizen may we conclude that a 'seizure' has occurred."198 Years later Justice Stewart proposed a similar standard, that a person has been seized "only if, in view of all of the circumstances surrounding the incident, a reasonable person would have believed that he was not free to leave."199
This asshole was seized, but he was not detained. Two different legal concepts.
Now, was the cop a dick for not explaining the difference? Yep, but frankly he isn't required to do so and the driver was being a dick to, so **** him.
Your amateur " I know everything" is a fail Quantam Windbag.
You simply don't know everything.