Think of short call as essentially the same as being assigned a trip. They're not pulling someone off it if they can find anyone else to cover a trip. This includes paying someone premium in order to crew it. They treat us short call folks like we are gold. Very reluctant to pull us off it unless they have no other choice.

Unfortunately that means they often won't allow us to go unreachable for a brief period (i.e. to commute home) even if we are no longer "useable" to be assigned a trip in that window. 🙄
But that's another thread...