Oh I don't doubt your last paragraph at all. Reading him here and reading his website tells me about all I want to konw.
Reminds me of Fulton Armory quite a bit.
I"ve only used SSA brass, in 6.8 so I have no dog in the fight. I can't actually comment.
I can say that if the flip were true and you tried a load proven in a lot of brass, in 223, and put it in FC brass you'd be upset for sure likely.
The problem with wildcat stuff is you have to know a LOT more about things than you think you do for when you hit a bump in the road. For normal cartridges thats all been worked out behind the scenes before release.
Tough issue this. Customer service is a key, and even if the customer is wrong, you should generally do the best you can to satisfy them. Unless they are completely stupid and a moron, the only way to do that IMHO is buy the upper back, shut the case down, don't sell to that customer again and just move on.