they are just reading 75 character to be excelent in there checker.
Really it's just 75?
I think the most useful feature is checking potential activity. I don't know of any other way to do it.
It's correct the checker just sue you for making a post more than 75 characters and you will get excellent but if less than it, you will get poor, or medium level. but the checker is can't become a standard for giving a rate for the account.
Post quality determined by account estimators using ration of posts bigger then 75words and shorted then 75 words