Regardless of the semantics of what we call theft, or whether theft requires denying somebody access to some good, there's an ethical issue with copying other people's stuff without permission. If a person breaks into another persons home and makes copies of all of the documents in their home private or otherwise, they've at least committed a crime in the form of breaking and entering. But if a person is invited into another persons home, and then without pemission copies all of the documents in the house, that still feels like a wrong act? Like, if you invite me into your house and I start copying down your personal journal, your family photos and other stuff you have lying around, to me that sounds like I'd be doing something wrong by you?
Edit: I do want to point out here that I'm not saying piracy is inherently wrong/bad or never justified.
Literally nothing in my post claimed that, or even really implied that so I'm not sure what your point with this is?