Well, we all know about the Spanish love of paperwork and bureaucracy so it really wouldn't surprise me to find out that this is true. It is still quite mad though.
A cousin currently has her property up for sale, she has owned it over 10 years so must be on a different passport now, if she gets a buyer I will let you all know if this turns out to be a problem.
Edit: Just spoken to her, she was surprised to hear about this and has not been advised about it by anyone, including her selling agents. We will see.