There's a continuum of both on-call conditions and a continuum of "whatever I like". Some on-call is basically getting paid for doing one thing a month. Others

There's a continuum of both on-call conditions and a continuum of "whatever I like". Some on-call is basically getting paid for doing one thing a month. Others are reliably going to require work. Some "whatever I like" is being at home idling, others are "cave diving in another country". In the middle there's plenty of space for compromise, because you can find a happy medium where both are satisfied.