There is a time limit for how long after the initial interaction/road side test until they administer the actual BA test. If they exceeded the time limit, they broke process/law/precedent/whatever, logic does not apply to the legal system just the rules.
It has nothing to do with the law but BA increases as your body processes/metabolizes the booze, then it goes down. Back in the day one of my classmates was pulled over leaving the pub. He had just pounded back three pints after class (chugged), he was pulled over right away and passed roadside (but likely stunk of beer). They knew he was drinking, they took him in and kept administering the BA until he failed. He won in court (but lost in the wallet, costs caused him to drop out) as he was something like 15 minutes from home and it took 45 minutes until he was over 0.08. He was never impaired behind the wheel and would have been home before we was.... that was in the early 90s for what it is worth. The above mentioned rule also did not apply to him as he was under the time limit. I doubt this was the case for the truck driver and his BA was going down.
