Just that the arithmetic mean is the one that has been traditionally referred to when assesing the succes/mediocrity/failure of a spawn. People are used to hearing it--when they hear "3.92" and don't know that it's the less familiar geometric mean being used, they tend to think that it's a disasterous spawn rather than a mediocre one.
It was also the one used by ASMFC to end the commercial moratorium--there had to be an 8.0 average over a 3 year period before the fishery was reopened.
The 26 recorded in 1989 accomplished this all on its own
And I mis-spoke the arithmetic mean for 2009--it's 7.87, not "a little under 10".