No- there were a few that had FC averages comparable to Pietersen that didn't get much of a chance because of the settled nature of the test line up.No. Late-40s, yes, but not mid-50s. Had Pietersen been returning those numbers in any country, he'd have been in the side soon as a place became available (and even in Australia that happens often enough).
Stuart Law and Martin Love both come to mind, and neither of them failed when they did manage to get in, but couldn't hold their places. You could add Darren Lehmann to that list, too- he waited years for a (limited, as it turned out) chance, while averaging 55+.
Jaques is current example. He averages five more than Pietersen, and is no certainty to get the nod following Langer's retirement. If he does get the spot, then another guy with a 50+ FC average in Rogers will miss out.
Having a 50+ (which is what Pietersen has, not mid fifties) FC average hasn't guaranteed a test spot over the past decade or so.