Experienced the same thing at RSW, but it was a pink card and it only allowed me to keep my shoes on. Pre Check was closed.
I asked if I still had to go through the nude-o-scope and they said yes. I refused, so I got a pat-down. The TSA agent who patted me down saw the slip and told me I could have just gone through the metal detector since I had PreCheck
I told her I was told otherwise before the checkpoint, and was told to "remember it for next time". Ugh.