I had the same issue when a guest stayed 25 times, yes absurd that Airbnb were penalising hosts for generating more fees for Airbnb!!
It seems they have now finally started to address the issue. Firstly they tried to change the logic to %guests reviewing but this data flattening (from trips to guests) seems to have flattened the IT department (or business haven't defined the logic correctly) and now they seem to have removed the statistic completely. Does anyone have any news? Airbnb seem to make unannounced changes regularly.
Airbnb: please provide an update, and if you need any help flattening that data correctly please visit www.enex.net