I suppose it might be to discourage clamping by the seatposts and then swinging on it like a chimp to remove the BB, but then I can't imagine clamping it by the frame would be that much better.
Regarding workstands, I've got the Park PCS-10, which is basically a PCS-9 with.a posher clamp, and am pretty happy with it. It's rather heavy and doesn't fold particularly small, and there's enough flex that I wouldn't want to do anything involving big torques with it, but that's common to all clamp-type stands IME. For general fettling, gear adjustment, etc. it works well, and can be found online for a fair bit under the RRP.