Fox aftermarket is not Ford OE; completely different entity. Ford engineering specs the shocks, Fox builds them. Fox is free to sell shocks in the aftermarket as they wish, that doesn't mean they meet Ford engineering standards or pass Ford OE testing. Your example is equivalent to saying if my factory fuel injectors are made by Bosch, and I bought aftermarket Bosch high flow injectors, I should have no issues because it's still Bosch. Doesn't work that way.
The guy claims he had "front end issues" before the mods; the guy is a liar. Nobody in their right mind has a warrantable issue, modifies it to make it worse, and then brings it in for warranty work. That's like saying you have an engine knock, so you installed a supercharger and then it got worse so you brought it in for service. Complete ********. The dude in question is a hack and has a history of buybacks, or at least attempted buybacks. Due to CA law, people like him are able to work the system, which enables him to modify and abuse vehicles and then request his money back at the expense of the manufacturer and every other consumer. It's calling gaming the system, and he's clearly profiting quite well from his videos. The dealer screwed up by ever touching his truck in the first place, but that doesn't excuse the fact that he's committed warranty fraud.
It's a plain and simple case of fraud; buy an expensive truck, modify and destroy it, bring it to the dealer multiple times claiming a defect, collect repair orders, and then request that the OE buy it back under CA "lemon" law. I hope he goes down with his own ship.