That's not true at all. Condo prices rise just like single family homes. And when you own a condo, you own a fraction of the land it sits on.
I would agree that condos tend to be more volatile than single family homes. More of them can be built quickly and when real estate prices start to drop it often starts with the condos.
Seems to be regional. I'm sure condos in places like DC appreciate, but in my region, condos absolutely seem to depreciate on average. It's exceedingly rare for me to find a condo on Zillow asking more than it was sold for 5+ years ago.
I would agree that condos tend to be more volatile than single family homes. More of them can be built quickly and when real estate prices start to drop it often starts with the condos.