A PH will be shooting at any inbound dangerous game animal. He has the legal and ethical responsibility for the lives and safety of everyone in the party, and that will not be negotiable ahead of time. With respect to back up shots, it will depend upon the terrain and his assessment of his hunter. Unless an elephant is falling to a brain shot, virtually all PH's will try to follow-up even if he has Boddington as a client. I suspect most are much more likely to allow a buffalo engagement to play itself out if the bull appears well hit.
Very well put. From a PH 'ing point of view, you have this one spot on.