Hello @TheRogueDM
This can be confusing for several reasons, but communal items in larger residential communities (apartment buildings, condominiums, even gated community) can be eligible. Think pools, workout centers, playground equipment. These are all accessible by the people that live there and their guests. Not every wayspot needs to be accessible by every Niantic player.
The restriction for private property is actually for Single Family Private Residential Property (SFPRP). Your example does not trigger this restriction.
Please see recent Niantic clarification here: Private Residences, Farmland & K-12