I agree with you so let me rephrase. When you run into a cop like this that has ulterior motives or an agenda, it's best to do what he says or wants (to a reasonable extent of course).
If he wants me to get out of the car for no explicit reason? Sure. If he wants to open my door? Sure. First off, I have nothing to hide (maybe this kid did). And secondly, there's absolutely no way you can win by not cooperating and being difficult.
To your point, a lot of things aren't done by the book with cops, but I think people get too touchy now a days. They're convinced that by getting out of the car or opening the door (in this example), that it equates to some sort of admission or conviction of a crime. Or, they're so hung up on rights, that they decide to "take a stand."
We'll never know in this case, but it's likely that the cop would have explained to him at some point in time why things were happening the way they were. He wouldn't have cuffed him, towed his car, and brought him back to the station without one word. The explanation was imminent, but the kid was too defensive/militant/impatient imo. I feel like the kid being difficult set the tone for the cop to react to.
Hell, I'll even go as far as to getting cuffed and still cooperate. Honestly, what can you do? There's literally nothing that you can do in that point in time that will make it go away. Either lawyer up or resist. We all know what usually happens with the latter.
Unless you plan on being a martyr and settling in court for a settlement, just say yes sir and shut your mouth. Personally I'd rather speed up their "investigation" and be on my merry way.
I understand that we have rights, but I'm not going to test those boundaries when it's just me against a cop. You're going to lose.