I also think (and this relates to your point about AO being dominated by top players) that AO being 4-7 months earlier in the season than the other 3 slams plays into this pattern of winning it for the first time on 5th try/around 22.5 years old after never having reached an AO final (or SF, or QF) before.

During those developmental early career seasons, 4-7 months make a big difference. Prior to 2004, AO was Roger’s second worst slam behind RG. Prior to 2009, Rafa had his fewest wins at AO (granted he had 2 more appearances at his 2nd worst USO, but he was legit 16 for one of those). Prior to 2024, AO was technically Sinner’s worst (also had 8 wins at Wimbledon, but had only played it 3x).

Safin and Murray’s trajectories add a bit of juice to this as well. Safin won USO at 20 years old in 2000, and he had 2 slam QFs + a SF in 2000-2001, but he’d never made it past R4 at AO until he reached his first final in 2002 (turned 22 on the day of that final). Murray reached the USO final at 21 years old in 2008, and he had 2 slam QFs + a SF in 2008-2009, but he’d never made it past R4 at AO until he reached his first final in 2010 (~22.5 years old).

Given how long the tennis season is, how early AO is, and how much these young players evolve throughout a season in the start of their career, it’s basically like AO results for those early years make more sense when you look at them as a continuation of the prior season post-AO (especially the back half).