Perhaps not so interesting question after all. But the question was triggered in my mind by the in my opinion inaccurate IAAF article.
In any case, my reasoning (having now looked up the exact dates for world records) would be:
- 100 meter WR holder always had the fastest average speed until May 7, 1965, when Tommie Smith ran 19,5 in the 220 yard (straight) - which would "equal" either a 9,7 or a 9,8 hand timed 100m.
- In 1977, with the move to automatic timing, the fastest average speed "became" Tommie Smith's 19.83 200 meter WR (9.915), followed by Mennea's 19.72 (9.86).
- On August 30th, 1987, Ben Johnson got the fastest average speed back to the 100 meter world record holders with 9.83, but that reverted back, to Mennea, in 1988 (or 1989 - I can't remember what the date of pre-1988 results annullment was).
- Carl Lewis tied Mennea on August 21st, 1991, with 9.86, and Leroy Burrell took the "title" completely from Mennea with 9.84 on July 6th, 1994.
- However, it didn't take long (just until June 23, 1996) for Michael Johnson to run 19.66 (9.83), and then 19.32 (9.66).
- On August 16th, 2009 Usain Bolt and his 9.59 made the 100 meter WR holder again the man with the highest average speed in history (Bolt himself already had the highest average speed in history, of course, as the 200m WR holder with 19.30 (9.65)).
So in the past 47 years, the 100 meter WR holder has only been the man with the fastest average speed in history for about 9-10 years.