Countless companies and industries enjoy making up scary stories when it comes to justifying their opposition to making it easier to repair your own tech. Apple claims that empowering consumers and bolstering independent repair shops will turn states into “hacker meccas.” The car industry insists that making it easier and cheaper to repair modern cars will be a boon to sexual predators.
A blown fuse there is a pretty good indicator that the wrong kind of charger was used, which actually warrants a warranty loss.
Either that or a small power surge happened. Or the battery was defective. There are multiple things that could blow that fuse, and having a blanket “blown fuse = voided warranty” policy is stupid.