Is it the stats that Pet Journal Enhanced lists? If so I think it's because these stats are predicted for a low level pet and could be inaccurate once it reaches 25 (not by a big margin but some people want to be sure)
I've noticed that occasionally as well. I think, like other folks are saying, it's just because the add-on can't determine pet breed based on the current stats. Gain a few levels, and it should revert to normal.