Oh, good God. If that’s the case, the law is an a**.
It’s a matter of consistency. It has alcohol, not much but some, if it’s enough alcohol to have the age limit applied then it’s enough alcohol to have the open container law applied. Pretty logical and easy, the ass here is the guy that thinks he should be a special case, he bought beer, and drank it in his car, it’s illegal, he knows it. He should stop wasting everybody’s time and pay the stupid fine already.