They think they've outsmarted libertarians when they've only engaged in bizarre definition. Effectively what they are saying here is that opportunity to use unowned property is an ownership stake, which is obviously false. I could use my savings to put a satellite into orbit, but I don't. Does that mean I own the prospective orbit of said satellite? Of course not. Similarly, opportunity to use is not ownership, only first actual use (improvement) or voluntary transfer confers ownership.

Jacobin wants this to be true desperately, as if it is, commie theft is legitimate; as everyone who ever had a possibility of touching a piece of capital owns it. As an aside, it's entirely possible to have a contractual commie-style property ownership regime (where any use implies voluntary transfer, enforced as a deed restriction). They'd rather have an incoherent system without property though, as it justifies their darkest desires.