If the guide is passionate about a type of bullet, he should tell his clients what bullet they should shoot shouldnt they? Also, shouldn't the guide have his own set up that he is confident in for those situations?
I guided for a while, never occurred to me to ask what bullet a client was using. Knew cartridge, rifle etc and our sheet had recommended bullets, factory loads for many Cartridges. Never had anyone who was hunting moose or bear show up with "Target" or frangible bullets. We also didn't permit shots farther than 300 yards on moose and 200 or less on bear so there weren't clients trying to setup for long distance shooting at large game.
To be honest,if we were chasing wounded bear and there were two of us, we usually left the client and went in ourselves. If you only have one guide with a client you will need to rely on the client playing his role as two are almost always better than one. As far as the guide having his own setup, you obviously haven't tracked too many wounded animals. Even though the guide has the right gun and ammo for backup you can't count on him being the one that gets to take a shot. Wounded bear often come in from the side, not straight ahead on the blood trail, that is precisely why you want one person tracking blood and one watching your perimeter.