I've seen those valves, but every time there is also a big ass gate valve just upstream.
Throttle valve that actually shut off flow are common. Throttle valves that can be counted on to shut off flow are nonexistent. I've seen hundreds of globe valves that actually give you a bubble-tight seal and dozens of globe valves that leak like a barn door, but I still stand by the statement that it is poor design to rely on them for isolation.
David