It's a 2014 Halloween Advent pet which is apart of a set. So no, it's not a bug, as the rest of the foxes in the litter are not PPS. Link: archive/2014/Halloween/Fennec%20Fox
It's pretty common for pets that don't have any growth stages to be missing the PPS label on the image of the pet, because it's pretty easy to figure out that it's PPS without the label. However, even these pets should have a small explanation of PPS on their page. This fox is missing that explanation. I recommend you send in a help ticket or post in this thread so that staff are more likely to see c: