Airbnb seems to be going around in circles on the SH / Plus criteria. We started with 80% 5* which strangely allowed 2/10 reviews to obviously be bad. That was probably a good compromise, and kept everything attainable.
Then an we decide to go to 4.8 avg. Now you anything below 3* will have a devastating year long impact. And oh, we will also make 4.8 avg required for plus so you better start putting up with whatever guests want.
Now we realize that maybe this will slowly destroy the host community, so we use some new algorithm to eliminate the outliers.
I'm not sure Airbnb is ready to IPO yet...