My big worry is that the dealer or zone manager might look at the maintenance records (and type of oil used) and use that as an excuse. Certainly UOAs could be a useful backup, but that doesn't mean the dealer/ZM will accept it when they've already made up their minds that they can deny a warranty claim because they have an "out". Let's say you've run counter to manufacturer's recommendations for oil change period and API approvals. They'll point to that and say you haven't kept your end of the deal, whether or not it really caused the problem.
I doubt that there will be any oil related engine failure within a warranty period. The problem will be if there's a mismanufactured part or design flaw, but the manufacturer's representative might paint the extended drains as a contributing cause. It seems reasonable that the manufacturer must show cause and effect. In the US, the FTC and several state laws even say that the manufacturer must show cause and effect. That doesn't mean the manufacturer won't refuse to do so with the idea that the carowner won't go through the trouble and expense of hiring a lawyer.