I agree and have also mentioned this issue in the community. Although someone will post telling you its only a small issue when you have otherwise reasonably good reviews -- but you still get the nasty gram email from AirBnb that the last review was low and if it doesn't improve you'll get removed from the listings :((((. Also, they say that superhosts get top rankings in searches - SO IT DOES MAKE A DIFFERENCE IN THE BOTTOM LINE.
I keep track of each of the star categories along with the combined stars for each trip. I also take screen prints of this since it seems to change for no rhyme or reason. Example:
11/15/2016 - stats said "4.5 overall (5 star trips – 57% of your trips (80% required)"
1/13/17 says 4.5 (5 start trips – 61% of your trips)
Not sure why my rating changed, when I had a 2 month stay beginning in November and ending 1/14/2017. There were no new reviews but the % went from 57% to 61%. Makes me think the calculations are not accurate?