On pl.wikisource each correction level means that another person did the correction again. The green status means the page was corrected three times by three another persons.
Corrected, not read.
In my opinion Big Green Button Correction is useless. New users can click only for stats, not for proofreading. And nobody would check it again, because the book would be finished.
We are asking new users to validate the pages for the second time (from red to yellow level): new users can learn how the templates and raw codes are working, but when they do something wrong, an experienced user would check it one more time -- to make it green. If they would not edit the page, they would never know how the templates works. So they would not become a better editors...
We all can do only red pages, why not. We'll get a "perfectly readable and functional book" with some errors. But should we give its the same status as a proof-read three times book? Green status means "almost perfect". We shouldn't make green pages automatically, only to make our stats better.
Correction without correction is not a good idea. It's a lie.
Wieralee