You paid a fine, you were CONVICTED. That’s what a fine is, it’s a finding and a penalty. A conviction.
That was possible because you were the courier at the border. You were pretty easy to investigate.
Unless you’re a U.S. finisher or the GB coordinator receiving hundreds of kits at a time, for which CBP might pursue an investigation to contact the addressee, merely having a package with your name on it seized at the border does not meet the elements of the crime and will not result in a fine and thus not result in a conviction. They’re not gonna come knock on a random person’s door who purchased a few kits to initiate an investigation and fine you, convict you.
The fear mongering is really ridiculous.