No, they can not ask and find out. First of all, many borrowers do not know an AMC is used, so how can they object? Second, if an AMC asks the appraiser, the AMC engagement letter nearly always has language in it that the appraiser is not to disclose or discuss the fee.
so how could a borrower care about something they do not know. The borrowers who did manage to find out have filed multiple lawsuits. Personally, my interest is far less in addressing any harm the borrowers think was caused by non-disclosure. That is for the lawyers and courts . My main interest in the lawsuits is that they might finally get the issue out in front for the public. Banks do not care about the appraiser, but they care about bad publicity.
The lawsuits (look them up ) contains phrases such as "unjust enrichment" to the AMC because of the large chunk of the appraisal fee they keep. One lawsuit compares their fee to usury.
If the AMC's are shown to be charging fees that are unjust enrichment, at whose expense was that ? The appraisers.
you mention the past 40 years. For decades, the fee split of the bundled fee in apprasials covered small amounts for misc faxing or messengers etc. AMC's if they were used, tended to mark up the appraisal a small amount, about 10%. That changed overnight when the HVCC created incentive for lenders to use an AMC and the AMC;s siezed the moment to charge big chunks for their service, since the borrowers would not know and the lenders were okay with it.
The lender does not pay for the appraisal, the borrower does, so the lender does not save any money whether they use an AMC or not. The lender does save some money for admin by not runnign their own appraisal panel. But the sure as heck do not save the $200-$300 a report the AMC's gouge for themselves by low fee bids to find the cheapest appraiser fee.
The lender might save $50 a report if that much, since AI and computer software can QC review, assign on a rotating basis, send payment etc.