If I submit my OC's hairstyle will Subeta now weirdly owns apart of my OC..?
No. They just own the wearable. They have to have this rule so that people can't sue them for using their art if they leave the site in a snit.

A thing to consider however is: If you're submitting something very unique to your character, even if you keep the item private it doesn't prevent other users from using that item in the wardrobe or outfit features.
So if you'd be uncomfortable with other users potentially making HAs / outfits of their own 'characters' that use your OC's hair, I recommend not submitting the item.
that is... quite concerning if someone used the hairstyle to make a whole new oc, imagine two oc's standing together having the same unique hairstyle without knowing each other, brrr..
I might change the color up cuz I already drew that and don't want to waste it lmao.
Yeah it's why I've never put my own OC items onsite unless they're not super unique. I know there was a problem several years ago of someone putting a very unique piece of clothing onsite and being upset when they saw another person had made a pet / character using the item. :S
oh dear, must’ve been stomach twisting to find that out. How did that end?
We were told not to put items onsite that held that much importance to us. Once it's onsite, it's available to everyone. Staff does not punish users for using existing items or features.