My guess is the lab is honest. They test what they are given. I've been involved with 3rd party testing and inspections for a dozen years. Every quarter an inspector would come un-announced, take random samples and send them to the lab. If you want to cheat, it is very easy to control what is sent.
Would have been interesting to see the comparative results, but my guess is their lawyers don't want to get involved. It was never said if they were contacted.
I feel so much better now.