Why should an appraiser drive the comps?
Well, to quote the fictional character Dr.House "People lie". Real estate agents are advocates for as high a value as they can get without outright lying, but some obfuscation is the norm.
Mr. Evens gives a number of prime examples here I feel warrant repeating, and to add my own touch I will try to explain why and give similar cases.
One of the photos looked like a single family home from the angle taken by the Realtor. It is actually an attached condo, appraiser didn't know that since he did not inspect.
All MLS photos are suspect because most Real Estate Agents will try to depict the property in the best possible light, such as: depicting a side-by-side duplex or condo as a SF; using interior shot or stock building photo for a high-rise condo (rather than the specific unit); ignoring or concealing deferred maintenance; etc. Photos can be misleading. I can't tell the number of properties I have seen in MLS marketed simultaneously as SF & condo or Duplex & condo.
Another comp was of a photo that was a proposed construction....."if you want to buy our overpriced lot we can build a house that will look like this". The parcel is vacant land
See above but this one deserves special call out as it is typical for builder properties in general. Even if actually constructed (and much less chance of that toay) the LEAST oddity I have seen is the exact same model / layout but flipped. Sometimes extra features, such as a stone facade, are different, but sometimes the actual building is a completely different model altogether and unrecognizable except for address. Remember that a stock MLS batch is generally run off prior to construction then exact model and features added later therefore a builder MLS listing is often no way shape or form accurate in reality.
four of the homes had wrong GLA
A good residential appraiser should be able to roughly estimate GLA just by inspecting from the street (if they can see at least 3 sides) and thus know if the GLA has been doubled by including basement or such.
and finally one home was listed as a golf course home that was surrounded by a cornfield....the golf course is down the road.
Lake view, lake access, golf course view, golf course access, yada yada yada. Until the comps are acually driven the view/access is not verified. I have seen listings of "lake view" where the view is 5-8 blocks down a city street if you force your head tight against the glass and make a wish on a fairy. Another favorite is water view through a copse of trees "well, when all the leaves are gone you can see 2 sq ft of water through that small gap ...". The list goes on. Aerial photos can show distance and location fairly well but it take a human on site to determine view, degrees of view, etc, and determine appropriate adjustments for it.
I have also seen the opposite: view of industrial area, view of gravel quarry (through the dust cloud), view of city dump, etc. Again, aerial may give some indication but the exact detriment has to be seen (and often smelt) in person.
So, I think Mr. Evans made a good case with that example and my additions bring additional support to his reasoning. Good luck and goodnight!