"You cannot claim this city because you do not own some of the content used to create it."

Agreed, this is super sketchy. Apparently you don't even need to plop any DLC content to restrict. By simply claiming a city with DLC added to your account you're restricting it from those who lack the DLC. It also goes directly against their claims that standard users can mingle with deluxe users without any limitations...which is turning out to be a lie.