You guys have totally missed my point.
For the h2h to mean anything, Nadal needed to actually get far enough in those slams I mentioned to stop Federer.
He wasn't able to, Fed leads 17 > 11 and thus the h2h is meaningless.
If Nadal ends up with more slams with Fed, the h2h will be a big deal. Until then, it's not.
Why would it only become important if Nadal has more majors than Roger? I'd argue if Nadal had more majors than Roger, H2H would become less important because, going by history, it would be even more lopsided. I can see the argument that the H2H can be used as a tiebreaker if two players have almost the same number of majors like for Lendl-Connors or Wilander-McEnroe.
Look at it this way: Muzza leads 9-8 in the h2h. He wasn't able to stop Roger from winning any slams. The h2h means almost nothing.
It means nothing because Murray hasn't won anything.
Nadal leads 18-10 or whatever it is. He stopped Fed from winning a few slams, but also wasn't able to stop Fed winning a shitload of slams.
Nadal stopped him seven times. And again, Nadal doesn't have a 100% win rate against Federer so to expect him to take most of Roger's majors is just silly – especially when most of Roger's majors came Pre-2008 when Rafa was just a clay guy. If we take it from 2008 onwards, which is the date in your original post so I don't know why you're still asking why Rafa wasn't able to stop him from winning the "shitload of slams" Roger won in 04-07, Roger has since won five majors but Rafa stopped him from winning four times.
If you flip it on its head, Muzza has a winning record against Fedsly. HOWEVER, Roger has won when it mattered, LITERALLY costing Muzzbot 3 slams.
Therefore, for Muzz, the h2h means dick squat, because it didn't gain him slams.
How is this "flipping it on its head"? But anyway, Murray has one measly win more than Federer; Nadal has eight over Roger; big difference. Nadal is also 7-2 (4-0 since 2008) over Roger in majors so Nadal has won his share when it mattered. Using your wording from above – Rafa has literally cost Roger 7 majors – so how does the H2H not become an issue?
IThe h2h by itself doesn't mean anything in the GOAT argument until it costs someone slams (or in Fed's case, the overall slam record).
A lopsided H2H becomes an issue when the two people in question are greats of the game. Nadal cost Federer seven majors. Federer cost Nadal two.