One does not actually need to have the actual hardware for forcing a driver installation on Windows, it just needs to be correctly signed with a trusted certificate. Now, that it has been done once, expect attackers to troll through thousands of still trusted hardware drivers for devices not even in production or out of support with similar vulnerabilities.
So no, the attack does not rely on you having a Gigabyte mobo, Gigabyte mobo owners may be even better off, since attacker has to do an extra step for downgrading the current driver without the vulnerability.