That's different than what is necessarily going on with Disney's system. TSA randomly does explosive residue checks. I just went through first time with pre-check on Friday and randomly was selected for my cell phone to be swabbed,my husband had gone in front of me and the TSA agent had told me "oh looks like you got randomly selected here one moment" and then I was directed to get my cell phone and only my cell phone (I had a kindle e-reader too) out of my personal item. So it is "resolving" the alarm but the indicator has nothing to do (in this case) with patting you down as it's not related to your person. Now sometimes they do hand swabs for explosives too but they don't generally do a pat down just need your hands.