Perhaps it is as simple as some providers having a different view of their volume, body shape, allure, etc.
For example, imagine if there is a provider who is proud of her 100 "Yes" reviews in 3 months but she decides to slow down to 10 clients a week... Even if they are all on the same day, in her mind, she is now low volume.
Or perhaps there is a bat-shit crazy cat lady who wears so much makeup that you wonder if its paper mâché... She considers herself beautiful and mesmerizing but she's needy and unstable so people just chock it up to fucked up hobby luck...
Personally, I wish ISO worked but it's just not worth sifting through all the spam it generates...