Second, its not my personal position or nothing I would ever do or condone.
Third, standard I am not an attorney disclosure.
The problem is you have to prove that is why they accepted that offer. The seller can sell personal property outside of escrow and it would be difficult if not impossible to tie the two together. As long as it is outside of escrow the seller technically is not receiving anything from the sale.
The seller can submit whatever they want to the lender who makes the decision to decide what they will acept. The seller is under no obligation to deliver a best or highest offer and the lender is under no obligation to accept any offer even if its above FMV.
I do agree that it is wrong and maybe even criminal but I just dont know how you would ever prove it.