I've updated about 15 xci games via OFW, no problem as yet. I can't see how the cart's unique cert would be used in this process. If you had multiple copies of the same game cartridge for some reason, maybe you have multiple switches, you wouldn't have to make sure you always used the "correct" cartridge in the same switch. Different cartridges wouldn't create multiple entries in the horizon menu, they would share the same icon/save data etc. so the header is probably not used as a part of that system.
Have any of the proper experts in this area actually looked to see if the cert for the cartridges is stored in eMMC when the game cartridge is first inserted? If it isn't, then there is no way that cert info could be sent to ninty when an update is requested, because you can download game updates without having the cartridge inserted.
Have any of the proper experts in this area actually looked to see if the cert for the cartridges is stored in eMMC when the game cartridge is first inserted? If it isn't, then there is no way that cert info could be sent to ninty when an update is requested, because you can download game updates without having the cartridge inserted.