Yes it is. Ralph has basically 6 real RGs, and even if you consider his 7 RGs, some people consider Borg as the better clay courter,if not its a tie. Borg didn't have the luxury to moonball weak 1HBH like Ralph so he had it much much harder to dominate at RG.
Ralph's 2011 RG has a big star on it,a widely acknowledged fact. Look as much as I like Ralph I can't quite crown him the clay GOAT cause that would be injustice to Borg,sorry.
Even Borg said Nadal is a better clay court player than he is. Nadal only lost ONCE at the French Open the guy is invincible on clay. Look how many times Nadal has destroyed Federer in the French Open final. Nadal also has more French Open titles than Borg. Come on, face the facts Nadal is superior to Borg on clay.