They only way you'd ever get the truth is to have hired an attorney, sued them and asked that question in discovery where the WCO's would have to answer under oath andexplain everythingthat influenced them. That's also the only way you'd ever find out if the stop was legal or not.
Just because there might be a situation where such a stop would be lawful does not mean that it always is. These things are decided case by case.
I am assuming that you are not made out of money so I guess you'll never know.