I am going to dissent on the basic premise here. I don't think that Splitter has gotten much better over the last three seasons. He has always been this good. He just has gotten more minutes. His per 48 minutes stats from his three seasons in San Antonio have been about the same.
Pop has said several times that Splitter has been doing what he is doing now all along, the latest being after the Golden State game. He was saying the same thing last year as well. The only big difference from season to season is a steady increase in playing time.