More like hardcourts are not real surface, tennis used to be played on clay and grass. Imagine Nadal in an era where USO played on clay. Noserer would have zero US Opens then
Borg was one of those rare great players who was good in both Clay and Grass. How many Australian Open and US Open did he win? Australian Open was played on Grass till 1987(Then converted to HC slam) and US Open was played on Grass till 1974 and on Clay from 1975 to 1977. His biggest success at AO was reaching 3rd round in 1974 and this was the only time he played there. He was the runner-up four time in US Open, once in Clay and thrice in Hard.
So, tell me the same thing again that Noserer would have zero US Opens then. And imagine again if Rafa really would've won US Open since it was held on Clay for there years.
Now imagine how many Grandslam your Noserer would have had if he played on that time. I mean, Australian Open was played on Grass. US Open was also was played on Grass till 1975 and then on Hard Court from 1979. And of course, how could I forget, the Grass classic, Wimbledon has always been played on Grass. And they were played on real Grass back then, not on some slow-like-sand Grass which are used these days.
Now count Noserer's slams and Rafa's slams.