I thought about that as well, but these are on fixed racks that cannot be easily moved, they would have to pick up each pot individually each night so highly unlikely. The garden center also has a section that can be walled off and lightly heated and a section that is always open air, they are in the open air section.I often look at what stores have sitting outside to judge if it's warm enough to put out certain plants. So in most cases that works pretty well as a guideline. The only trick is some places push plant displays back under cover at night, or large nurseries will close up certain areas at night, but that's less common.
I did look very specifically as to what racks they were on and where exactly they were and the structure of the area because I suspected they were being protected somehow but I didnt see any way they could do that in a practical way.