I don't really agree, but I can atleast see the argument. Personally I think being 0-1 vs Krajicek at Wimbledon (which IMO might very well have been 0-2 if Krajicek had held his break lead vs Ivanisevic in the 98 semis but alas we will never know) is arguably worse than going 1-3/0-3 in finals vs a fellow grass great baseline expert on slowed courts, while well into your 30s.
I do think even though Federer has firmly surpassed Sampras in every grass stat, that Sampras still has a legit argument as the best grass courter as well though. If one goes beyond stats it is a very close call between the two. Borg is just behind both, but he shouldn't be forgotten either, to dominate grass like that in the era of truly fast grass and serve volleyers as a clay court god is just amazing. And totally unlike Nadal or Djokovic completely changes his game for grass which is amazing. Laver is up with Federer and Sampras, but I prefer to put the mostly pre Open Era greats into a seperate discussion with other pre Open Era greats. Djokovic could come close if he keeps winning Wimbledons, but I don't think he would ever quite make it to #1 or #2 for me no matter what. He just benefitted too much from the slowed down conditions on grass.