This is just a photographer's identifying photo. I do it all the time when photographing multiple subjects. The first photo I have the subject hold a placard identifying them. Then when looking at my proof sheets I know all the photos following the placard are the same subject.
It's especially helpful at auto shows. First a picture of the placard, then pictures of the vehicle.
As to why they would use the identifying photo for the card? Maybe thought it'd be funny?
Someday my cards may double in value and then be worth half of what I paid for them.