I also don't see the benefits of not describing how LC assigns credit grade. It is going to reduce the reliability and trustworthiness of credit grade as loan quality proxy.
The more concerning for me is the presence of borrowers with current delinquencies, previous bankruptcies, tax liens, collections and Lending Club credit grade model not accounting for these factors in assigning credit grade. I understand expanding borrower base but the loan quality model should account for such negative factors.
Right now, too many such loans show up in grade A to C. I believe no lender will rate borrowers with previous bankruptcy who runs up credit card balance again as same risk as the borrower who has no previous bankruptcy and does the same.
I think it's because they don't want lenders to know how many "less than prime" borrowers they are making loans available to now. I am a bit of a pessimist though. I don't see what advantage/disadvantage they would have in the market place for publishing their criteria besides making their lenders more informed investors. Prosper doesn't copy LC rate setting model.