Fact 1: Players those days got measured for their height barefoot. Instead of today when they are measured with shoes on, which adds to their height. So by common NBA media logic, those "'6'8" centers would be 6'10 ft tall. Normal height for a Center in the modern NBA. Shaq is in fact 6'11 in real height
Fact 2: Wilt and Russell playing with short guys is in fact a myth. Here's a list of players in Wilt's era he played against 6'10 and up
Kareem Abdul Jabbar: 7'2"
Dennis Awtrey: 6'11"
Walt Bellamy: 6'11"
Tom Boerwinkle: 7'0"
Nate Bowmen: 6'11"
Mel Counts: 7'0"
Walter Dukes: 7'0"
Jim Eakins: 6'11"
Ray Felix: 6'11"
Hank Finkel: 7'0"
Artis Gilmore: 7'2"
Swede Halbrook: 7'3"
Reggie Harding: 7'0"
Bob Lanier: 6'11"
Jim McDaniels: 6'11"
Otto Moore: 6'11"
Dave Newmark: 7'0"
Rich Niemann: 7'0"
Billy Paultz: 6'11"
Craig Raymond: 6'11"
Elmore Smith: 7'0"
Chuck Share: 6'11"
Ronald Taylor: 7'1"
Nate Thurmond: 6'11"
Walt Wesley: 6'11"
Fact 3: The low number of teams plays into Russell's advantage. The NBA in the 50s - early 70s had 1/3 of the numbers of players they do now. So the competition was stiffer. Ever seen the lineup in the all star games of those days? About 3 hall of famers on each team. Wilt would go against 3 hall of famers a night, no 90s Clippers type teams in that era. Imagine Durant, Wade, Kobe on the same team playing against Lebron, Carmelo, Chris Paul on another team