Most of the No No words labled by GSEs, I don't use. So no big deal and rather common sense not to use it.
I can see some having a problem for those who use coded words.
I am going to predict that eventually there will be two levels of appraisal:
1. The traditional appraisal, which will be protected from accusations of impropriety, by a kind of agreement that if a user of an appraisal report is dissatisfied with the report, he agrees to pay for an "Advanced Appraisal Report" - based most likely on MARS regression and some constraint based method. The fee will like likely be triple or quadruple the normal appraisal fee. The rules for the traditional appraisal will be between the property owner, lender and GSEs. With or without the intervention of an AMC.
2. The lender and GSE's would have to agree to accept the results of the Advanced Appraisal Report, if it is requested, under the assumption that the GSEs have received a Traditional Report that satisfied their guidelines, except for the final value conclusion.
3. If the lender or paying client of the Advanced Appraisal Report is dissatisfied with it in any way, - they can also challenge it in court (no the State can't be required or forced to give more than a cursory review of such a report) - but that would be a very difficult and expensive undertaking, ..... due to its complexity, and due to the fact that the appraiser is probably in this case the best expert around. Another expert with expertise in the subject market area, R, and non-parametric statistics would be indeed very difficult to find.
4, And the appraiser who did the Advanced Appraisal, will of course be in the strongest position in such a lawsuit - as he will likely be the one best expert on that particular report. --- Well, evenutally, I suppose, they will be able to run these reports though an AI system like Claude to get an opinion. But the appraiser himself can do that as well.
5. I would add that AMCs need to be taken of out of the picture, especially with respect to Advanced Appraisals. They simply do not have the required competence, nor are ever likely to.