The Gateway will only work to launch 3DS ROMs if the system firmware is version 4.1-4.5. One of the features of the Gateway (and clones of the Gateway) is called emuNAND, which is an emulated system firmware (think of it like dual booting the 3DS system firmware and the emuNAND). The emuNAND is capable of being updated to newer 3DS firmwares without fear of affecting the 3DS' main system NAND (which should always be on v4.1-4.5). What you read on their website is that the newest firmware provided full support for emuNAND version 7.1, this means the 3DS' main firmware (the system NAND) should still be versions 4.1-4.5 in order to even launch the emuNAND.
Even with emuNAND, Gateway users should wait to update it until it's been confirmed to be functional, which is why the team made it a point to announce the 7.1 emuNAND compatibility on their website.