Purging simple invoices after R12 upgrade

I've tested the purge process, and the only invoices that are purging are $0 invoices. I've gone through the invoice criteria, and I think the problem is the Invoice Lines. We upgraded to R12 in 2013, and when I click on the invoice lines, all of our old invoices prior to 2013 show the upgrade date as the last update date.  So we have invoices from 2001 which show a last update on the line being 2013. Is this what is preventing the invoices from purging?

Has anyone else encountered this? If so, is there a workaround?