It is the personal inspection vs another party doing it.
When an appraiser inspects a subject, they are not just performing rote tasks, they are gathering vital impressions and opinions because they compare the property to the thousands of others they have seen in the field . Also the appraiser frequently interacts with a RE agent, owner or builder on site and gets information.
The appraiser inspecting the subject develops an integrated report. When the inspection comes in second hand it is a piece meal report. Substituting a second hand inspection will yield "data", but it will never provide the same first hand impressions and feedback, which can distort final result. I often decide my value in a close call depending on what I observed at the inspection, and I know from experience, even with today';s good overhead maps, clear MLS photos, lots of data, that the impressions I form onsite are often different than how the property appears in notes, photos and on a map.
Having another party inspect subject for a 1004 is like paying another person to eat a meal for you. The person reports a list of "facts", what the ingredients were ,temp degrees and how large the plate was . But you still have no idea how it really tastes, and if it the meal is really better, worse, or the same as other meals .
The fast turn times for both the inspector and the appraiser at desk adds to the fast food assembly line new world these will bring. Sorry Fannie, a property valuation underwriting a loan for 30 years of an investment of hundreds of thousands of dollars to secondary market ( and affecting a borrower even tough they are not the client) is not the same as an UBER ride or ordering a pair of socks from amazon. Their willingness to sacrifice soundness of appraisals to emulate a click service fro a cheap consumer good is insane. However massive govt and corporate insanity at the highest level of financial and housing markets has transpired at various times over the yeas, so they are following a historic trajectory