You are right that climbing buildings is not directly comparable to free soloing rock. Each has things that make it easier or harder. Rock isn't "meant" to be

You are right that climbing buildings is not directly comparable to free soloing rock. Each has things that make it easier or harder. Rock isn't "meant" to be climbed, but the vast majority of free solo climbs occur after extensive roped rehearsals. Some people do "onsight"/climb without practicing with ropes first, but this is rare, and is essentially only done when the route in question is known to be easy. Buildings are more predictable and regular, but these guys seem to be onsighting everything they do, which is mentally very different.