Uuuuh... I know nothing about cc, but I was trying to make an accessory that went under the "hat" category and wasn't actually a hat, but it still caused hairs to look how they would if they were under a hat (hat chops). I however fixed this by going the sims 4 studio warehouse, clicking region map, edit items, looking for where it said hat or whatever and changing it to base and the value next to it to 0.
I don't know if that's what you meant when you said the "shape" was still there but hopefully that helps because I know the hoodie is not a hat but the hair is getting pushed down like it would if the clothing was a hat. Does that make sense..? Hopefully this is somewhat helpful, I have no idea if this will work in your case, but worth a try.
