I can't see into the world, but is he actually flying all the types listed? Look at column "in use" in his "aircraft fleet" page. It could be that he/she has a lot on order, or leased out, or in storage etc. None of these count towards commonality.
I can't speak for the beginners world, but in the real worlds then commonality over 100 aircraft and 3 fleets really starts to bite! So its good discipline even in BW to keep to 3, or better, 2 fleets. That leaves 1 unused fleet for fleet change time, eg 727 -> A320 etc
Simon