Incorrect sir. As a basketball coach, this is one of the essential facts that we teach to kids as early as possible.
You are NOT what you guard - that is just your defensive position. You are the position you maintain on offense. Amare Stoudamire is a PF on offense almost every time down the floor even though he may guard the center of the other team from time to time. Same w/ Bosh, Boozer and many others. KG does play C, even at his age, but playes PF more often. He is quoted as being very upset when Perkins was traded as he new that meant he would be asked to play C more often.
Plain and simlpe, PF is different than C - even in the Spurs system. Play calling is different. Who sets the pick up top for the pick and roll is different. Who lines up on what block and which side of the floor the 1st pass goes to depends on who's the PF and who's the C. The movement of the ball around the perimeter is different.
TD has always been listed as a F-C but played the PF role almsot exclusively when David Robinson and Will Perdue played C. Then it was Kevin Willis and Nesterovic, then Nazr Mohammed, Mahinmi and so on. As you mentioned, he has played C more and more as he aged and as different individuals came and went (Horry, Bonner, Oberto to some degree and even at times w/ McDyess) but he still plays PF some as well.
Regardless of all that, the domination by a C been pretty much non-existent since Shaq's decline (w/ the exception of Dwight Howard). You don't really need a DOMINANT center to win championships as the Lakers, Celtics, Mavericks, Bulls, Cavs and Heat all proved you can make it to the finals w/ dominant guards/forwards. Likewise, having a dominant C, even one playing as well as you say TD is playing, certainly doesn't put you any closer to a championship w/o the other pieces. Splitter isn't the PF that will put the boys over the top next year - the year after that, TD will be gone.
So, while your point is valid, it's also somewhat mute. The thread is about Splitter starting next year - who, in my humble opinion, plays more like a center. Whether he becomes dominant in the next few years isn't as important as the other pieces the team has (Leonard, Anderson/Butler, Blair, etc.) and whom ever they can pick up to play PF.