Welcome to the forum @Ranger
If you have submitted a report that has been rejected, you can appeal that rejection in Wayspot Appeals with a screenshot of the rejection email, and then you can give more evidence to staff there.
However, this does not sound like it meets removal criteria. The only kind of “private property” that is prohibited is SFPRP - single family private residential property. Here is a clarification on that:
The tool tip in the review flow also makes clear that Wayspots do not have to be open to everyone:
If the property owner does not want a Wayspot there, they can request that Niantic remove it through the form linked at the top here, which is easy find with a Google search, since most people don’t want to follow a link someone gave them. But this is the link: