Well, that(what spoonbot said) is what Compass said, initially at least. Maybe they did more later that they didn't publish?
I have lots of tires that don't hold air without sealant. I was surprised at how well the Schwalbe tires hold air without sealant - that is the only tire I have that has an airtight casing. With a high performance supple tire, the sidewall is just there to hold the tread in place. ;-)