Yeah, it’s not counted as an open[1] data, unless the uploader shows any proof saying “yes, no problem uploading a copy of that into OpenStreetMap…” Best if there’s a copy of any e-mail exchange between the involved parties.
Strange, considering boundaries are uploaded as closed, unbroken ways rather than split ways connected together to form boundary relations.
Hooray, deeper copyright rabbit hole!
[1]open here means you can view, manipulate and do almost everything including distribution or re-distribution of said data