That this appraisal is getting reviewed should put appraisers on notice - if they accept a desktop hybrid on the idea that it is "only" an equity loan for a 30 k pool, or "only " 500k loan on a 3 million property, the appraiser is still on the hook for the value or loss .
WRT equity lines of credit , which can be for "smaller " amounts, these are like second mortgage liens on a house. These kinds of liens are often sold to investors who contract them out for collection. If they do not get paid out of the short sale or REO, they pursue the owner and appraiser, and can go after people harder than the origination loan lender does, ( the origination lender usually gets the loss satisfied on sale thus far less likely to go after the appraiser for the $ unlike a second lien who will go to the ends of the earth to recoup a loss.