If Safariland defends and doesn't settle, I would expect that they stress that field tests are "presumptive" tests, and not conclusive tests, and are intended only to give an officer in the field a presumption that a substance may be the illegal substance. In other words, they will argue that the test is intended to generate a visible reaction when the test chemicals react with certain other chemicals often found in the illegal substance, with the purpose being to help officers determine if they have probable cause to make an arrest. Now, remembering that I'm a lawyer, not a chemist, I can imagine that there are chemicals common to meth that are in food products, given the hodge-podge mix of crap that goes together in the meth manufacture process. And, at least in my jurisdiction, field tests are not admissible for purposes of identifying a controlled substance, Proper laboratory analysis is required for a court identification. Field tests are just a tool, and I'm sure that the documentation provided with that tool will show that Safariland sold it as such.
Bottom line, the guy in the OP who was arrested (or more accurately the guy's lawyer) is suing the deep pockets, looking for a settlement. If the goal was to get real justice, they would have sued the agency that made the arrest.