If they've got shorter fins they could just be younger.
Alternatively their lineage may include some plakat genes, making the fins shorter. If you look at my avatar pic of Rembrandt you see his fins are very long and they are longer now that he's grown up a little more too. HM's generally have lots of finnage just because of the way they are bred.
So I'm still leaning to HM for little Savy
Besides, VT would still have that droop, the top of his tail wouldn't go straight up like that and he's got too many ray's. VT's only have 2 rays and I can see on his tail where it's already splitting into two rays and so they would split again a few more times. But we'll see when he regrows them