I hoped that for once you will be considerate of the conversation, but, "no".
Let us see what we have, and why: in 2002 Federer had his fist ever spring HC/clay court season, where he actually started getting serious results. You might not remember it, but I do: he had a very steady R4 or higher results up until the Miami tournament, where he managed to reach up until the final, after which his level understandably dropped, not being used to playing that long at that level. He lost early in is next tournaments, just to pick himself up , this time to win Hamburg.His next tournament was RG, where, again, his level was on the floor. Who beat him in the R1 there: the world #45. By no means a pushover, no? He had early losses at Wimbledon, Gstaad, Canada and Cincinnati , before picking himself up and having a decent performance at USO and till the end of the year. That was Federer's break through year.
Unlike him, Nadal had his M1000 and Majors breakthrough in the same year, so he achieved his higher level much earlier, so that was an advantage for him over both Federer and Djokovic, in that comparison, but I am sure that you wouldn't mind missing to acknowledge that fact, seeing the way you argue.
I proposed a method that to some extend eliminates that, but you were quick to get onto it, but without saying why. However I know why.
In your desperation you make the mistake to not apply your approach towards Nadal, so, let us see: I discarded also Nadal's results for 2005, after he won MC. However, even with your nitpicking, the results will stand so:
Nadal 8
Federer 6
Djokovic 4
So, Nadal has twice as many early exits as the player from his own generation, despite of maturing earlier, and a quarter more than Federer, despite of the latter playing for five more years.
So, even discarding the Majors level (which is a fair assessment for the reasons already stated), and your inability to defend your positions , leading to having to deal with multiple corrections, including correcting your own "unintentional" errors, Nadal is massively behind the other two, when it comes to holding against early upsets.
Instead of "debunking" the myth, now it is not a myth anymore , but a plainly explained truth, so thank you for the chance to show it to everyone reading here.