I think there's some ambiguity when you speak of "ownership of IP".

I don't think anyone disagrees that, when you create the first copy of a new work, that you own that copy (assuming it's not a work-for-hire or something).

There is definitely disagreement around whether you should be able to prevent other people you have given a copy from creating further copies. That ability is what it means to "own" a copyright. And I would argue that that is clearly not a natural right, though possibly something we nonetheless want to enable for some period of time.