This post that was quoted has been deleted.
Once again, you have to treat residence and fiscal residency as separate subjects. If you're not fiscally resident here but own a property, then you have to pay non-resident tax on the property.
Ref the 720, the legislation is messy to read because there are so many cross-references in one law to other laws, which makes it difficult to get a clear understanding. However, I think the following is the clearest instruction re the 720:
Orden HAP/72/2013:
Artículo 2. Obligados a presentar el modelo 720.
Estarán obligados a presentar el modelo 720, «Declaración informativa de bienes y derechos situados en el extranjero», las personas físicas y jurídicas residentes en territorio español, los establecimientos permanentes en dicho territorio de personas o entidades no residentes y las entidades a que se refiere el artículo 35.4 de la Ley 58/2003, de 17 de diciembre, General Tributaria,…
In this context, you have to read references to resident as meaning fiscally resident. What it says in effect is that (provided you meet the qualifying criteria) you have to submit a 720 if you're fiscally resident, or if you're non-resident and run a business in Spain. If you're non-resident and don't have a business here, then the 720 requirements aren't applicable to you.