It is absolutely necessary for the Shatnez lobby to explain what they’re looking for and what test they run to determine shatnez.
Arguments like this, from a “Rav”, demonstrate why this is a problem that needs to be addressed:
“I’m a Rav, and in my opinion, suits should be checked for shatnez.
30+ years ago I used to wear BB suits. Always got them checked and never found shatnez. Still think you should check it.”
Different checkers obtain different results. Your mileage should NEVER vary.