IMO "average lender interest" means the average amount of interest paid to lenders over the life of all loans made on the site. I see nothing intentionally deceitful here. It does not say APR because they do not mean APR. My understanding is that the length of each loan is variable, and because of that, the effect of the site's fees on "APR" will vary with each specific loan. "Average lender interest" is more meaningful to lenders than it is to borrowers, and I would imagine that it was a term coined for them.
I haven't been through the loan process on the site, but I cannot imagine that the exact terms and fees are not fully disclosed on a site like this. I just don't see anything wrong here given that the site deals in loans with many variables. At worst they are guilty of advertising a number that does not have a lot of meaning to borrowers, but again they have two sets of constituents: borrowers and lenders. This number does have meaning to lenders.
I haven't been through the loan process on the site, but I cannot imagine that the exact terms and fees are not fully disclosed on a site like this. I just don't see anything wrong here given that the site deals in loans with many variables. At worst they are guilty of advertising a number that does not have a lot of meaning to borrowers, but again they have two sets of constituents: borrowers and lenders. This number does have meaning to lenders.