Last month while heading to preclearance at T3 one of the yellow smocked greeters gave my girlfriend attitude when we tried to go to the nexus security lanes.
As we walked towards the nexus nook the greeter asked if i was nexus I said yes and continued to walk. She then yelled at my girlfriend saying she needed to have her nexus card visible. It was very bizarre. Funny thing was my gf was holding both our cards and the protective case was visible.

Most likely just a case of one low level person trying to maintain some authority, whether not it was theirs to have.