Not sure if this is intended behavior, but there is a ledge / lip in the pit that acts as a ceiling, preventing characters from getting thrown.
Here is a 17s video showing how Wraith was captured by the Lash ult, but hit the ledge and wasn't thrown like the other 3 characters were, and instead was able to remain in the pit and secure the victory:
Here is a 17s video showing how Wraith was captured by the Lash ult, but hit the ledge and wasn't thrown like the other 3 characters were, and instead was able to remain in the pit and secure the victory:
