I can certainly understand where 'initial disappointment' can happen, but it doesn't mean he has to be 'forever disappointed' get away from the Hornady ammo, and get into ammo that is a closer representation of the cartridges potential. All of the other cartridges you mentioned are also great cartridges, but the 7PRC definately has a place, and will do the job well. There are 2 or 3 custom ammo companies out there that will load for him as well.....he isn't stuck.
One other comment, finding someone to load for him would be a good idea since he chose a shorter barrelled rig. There is a lot of powder in that case, and to take full advantage of that you will probably need a faster burning powder than what factory ammo would provide. Same would be true for the other cartridges you mentioned would have been better choices.
I think he will love the rifle and performance in the end, if he just looks past the Hornady ammo