I do not know about "his" outfitter
Ryan, but I can tell you the way our PHs think about this...
For Eland, we always prefer a hunter who shoots a .308 properly to a hunter who could not hit a barn from the inside with a .338 mag (and there are indeed plenty of them). Seriously, this is not an earth shattering answer, right? Who would not???
This being said, still for Eland, we also prefer a hunter who shoots a .300/200+ gr or .338/225+ gr or .375/235+ gr or 9.3/230+ gr, etc. properly over a hunter who shoots a .308/180 gr properly. That too is not an earth shattering answer, right? Who would not???
This business of comparing a good .308 shot with a bad .338 shot is childish...
Here is the reality: if a hunter cannot shoot properly anything bigger than a .308, sure we will let him use it on Eland, and we will make sure that if he uses it his chances of success are very good. But he should be prepared to possibly pass the only shot he may have at the Eland of his dreams that day. And if that day happens to be the last day of his Safari, then, well, a responsible PH will still not let him take a tough quartering shot at that Eland that would irresponsible with a .308/180 gr but that would have been responsible with a .300/200+ gr or .338/225+ gr or .375/235+ gr. That's all.
As mentioned previously by
CoElkHunter, the difference between "him," the international client, and a local farmer or PH is that the local will be there the next day, and the next week, etc. to have a shot with his .308, but the international client will be back home and he will not have another shot for another couple of years, or maybe ever...
All of this should really not be hard to agree upon. A bigger gun with bigger bullet does not make a bad shot into a good shot - we all know that - but it seems a bit infantile to argue that a .300/200+ gr or .338/225+ gr or .375/235+ gr does not give you more options to take a proper shot than a .308/180 gr does.
To each their own, of course. I personally do not go often enough to Newfoundland or Africa to restrict my hunting to only perfect broadside shots at bayonet range, just because locals who live and hunt there their entire life have success with their .303 or 30/30 or .308 on 2,000 lbs animals.