Looks like the two known copies are exactly the same label wise. If you compare the Wouldn´t You Know labels they have the same markings and shadows around the spindle hole, the same dots/ink spots in the same places and so on. I guess it´s the same record being pictured with other photographing skills.
As far as I know SUN pressed in runs/batches of 300 records for 45 rpm singles before the mother stampers were worn out. Not sure how many you could go for with 78 rpm.
It would make no sense to press only one single 78, in my eyes. I cannot imagine Sam Phillips did that because it is not economically. Sam was all about making money back then. If there is one there must be more...but that´s just my guess.