As I’ve pointed out before, this is actually useful due to contamination, and the fact that you can’t label a product as gluten-free without testing either at the manufacturing or ingredient level.
Granted, “Gluten-free” was not always so regulated, and then it was often a crapshoot. I personally also would prefer they mention what sensitivity of test they used, e.g. “Gluten tested to be below 20ppm”–which is what “Gluten free” actually means.