No doubt their high-end clients don't like having their presumptions about the size of their buildings questioned.  The Chief Appraisers (or let's use the word Vice Presidents) seemed to go into convulsions at the thought of their MAIs doing measurements.  You have to wonder what terrible experiences they have had in the past.
No doubt, the various BOMA Standard measuring services available are the ultimate authority; for example,
	
	
		
			
				
			
			
				
				As-Built Drawings, 3D Laser Scanning, Scan-to-BIM, and Area Analysis for Real Estate, Architecture, Engineering, and Construction.
				
					
						
					
					www.xmeasures.com
				
			 
		 
	 
The MAIs have distinctly bureaucratic minds; they do what they are asked to and no more.  No sense of perfection here except to do what is expected, e.g., never offend high-end clients and cautious with all other clients ....  You see them struggling into the night trying to make their numbers bridge the gap between reality and the client's wishes.   Their business depends on it.
You see, the job of an appraiser is not what you think.  No, it is a political job:  Try to convince the client to be somewhat more reasonable, try to convince the reader of the report that your exceptions are justified based on your experience and nebulous reasoning, and so on.  And it's an Artsy - I can't think of an appropriate word, although scam comes close.  However, you'd be surprised; an excellent MAI can make what seemed impossible weeks ago seem flawless, given time and effort.   And who is wrong, who is right, - see if you can tell.
One thing I notice in the vicinity of MAIs is that I am in the company of some very elite and clever white magicians who know how to stay one step ahead with these complex calculations, often involving 10-20 or so Excel spreadsheets with their macros and formulas.  They excel in their field.  They are masters at their art.  That they ARE.  Making the Market Value match the Income Value match the Cost Value, making the Current Year MV not too much higher or lower than last year's, and so on.