Yes, and you can also throw in Navratilova who has said on record that she took to grass with ease despite not growing up on it. I've made this same point myself.
Where I differ is on Pete's sliding. I know this is often put forth as the explanation for his lackluster results on clay, but I don't think that's quite right, because while there are matches where he looks downright awkward sliding on the surface, there are also others where he seems on a much surer footing (his '94 Italian Open final against Becker comes to mind).
Instead I think the reason was more strategic and mental. IMO Pete never quite figured out the right balance between net and baseline play. He had to use the former judiciously, because unless your name was Rafael Nadal or Bjorn Borg you were not beating prime Courier or Bruguera from the baseline, at least not most of the time. Pete was gonna succeed in that daunting task 2, maybe 3 at most out of 10 times and of course we know he did just that not once but twice at the same single event ('96 FO), but this was the proverbial alignment of the stars: the courts were reportedly playing fast (though I doubt they were that much faster than usual), Bruguera was coming off an injury-ridden year, and throughout the tourney but especially against Courier Pete was inspired by the recent passing of his long-time coach Gullikson (in his book he discusses how strangely calm he was in the QF even though he was down 2 sets to none). In other times he expectedly came up short, as he did in '93 and '94, and as Becker had found out in his painful loss to Edberg in '89 when he tried to topple Edberg off the ground rather than engage him in S&V battles.
Which brings us to the mental/baseline part of the equation. Past net rushers like Panatta and Noah have shown that coming in can be a successful strategy on clay even against its best exponents like Borg and Wilander, but what's often left out of this factoid is that they didn't just storm the net behind every serve, but rather they patiently traded ground strokes with their opponents while waiting for the right time to move in. (I was once corrected on this very score by krosero, when I made the oft-unchallenged claim that Panatta beat Borg twice at RG with S&V.) This is probably what threw Sampras off the most, and in fact it explains why he had his best result at RG in '96 when he had this net-baseline balance right (the stats I've seen show that he had a fair number of net approaches, but not the kind of sky-high # that a full-on S&Ver like Edberg posted in his '89 SF). In his later years he was attacking the net more and more to an extent where the back court was put on the back burner so to speak, which made getting into that baseline groove more difficult, and I think this was reflected in his sliding we talk about so often. That is, he was constantly questioning whether he should be duking it out from the baseline rather than charging the net at that very moment, hence the unsure footing and the awkward-looking sliding.
That's what I meant when I said his sliding issue had more to do with his mind than with his footwork. In his late years he simply wasn't confident enough as to where to be on the clay court, and he needed someone to rein him in and stress more patience on clay so he could develop this confidence or right frame of mind. Unfortunately Annacone was not this someone, because if anything he was more of a net rusher than Pete and the brand of attacking clay-court tennis necessary to win RG was as alien to him as to his more talented but no less unaccustomed pupil. And when the right coach (Higueras in 2002) came along it was already too late and Pete was no longer willing to tinker with his game (or racquet).
