Ivanisevic's finals were all in the same slam : Wimbledon.
Chang in 3 different slams.
It was all in the same slam but it was THE slam. If a player is gonna win a major or come close to winning a major, they probably wouldn't pick AO, FO or USO, they'd probably like Wimbledon. Additionally, I believe that during the years Goran made the Wimbledon finals, the fields were loaded with anyone who could win it (even with Sampras in the draw).