Yeah, that's exactly the case. Boris Becker never won ANY professional tournament on clay, though he once had a match point in a final against a top clay player, Thomas Muster. He was so desperate he tried to hit a second-serve ace, missed, and lost it. I believe Sampras lucked out and won a minor, once, the Italian Open. Ivan Lendl was best in the world for several years and never won Wimbledon ... McEnroe never could win the French. As great as Federer is, he, hasn't won the French, either.
Perhaps with the IPT a line will be drawn not only between snooker players and 9 ballers, but 8 ball specialists?