Replacing the factory cloth upholstery with leather does not seem like a neutral act with regard to warranty. They add sunroofs. Replace suspension bits. Acura dealers were painting the ugly beaks on 4th gen TLs. Etc. Ad nauseum. I think pretty much everything they do besides installing the factory authorized accessories poses some risk that Honda will disavow warranty for whatever they messed with and anything affected past that. If you are the buyer buying one of these cars from a dealer doing this, you pays your money and you takes your chances.
If you have enough money, you can do whatever you want to a car. You want a gold steering wheel? Cough up the bucks and it can happen. I'd guarantee that dealership is offering leather seating as an add on, being performed at a lower price by a 3rd party then marked up by the dealership. This is why I get nothing done for aftermarket by the dealer, go direct and save.
Say they break the seat adjustment stuff while having it out to replace the upholstery. Say you get an airbag light because they screw up a connector. Those faults would be covered under warranty if the upholstery had not been mucked with.
