Correct. So strictly speaking about 2-1, what is "misleading" about weighted averages? Short answer nothing. Does it comply with Fannie Mae? Hint. Fannie Mae isn't USPAP. So you are not bound by Fannie rules by USPAP directly. That is, proximate, recent and similar are a fannie thing, not a USPAP thing. 2-2(a) - (viii) would be more relevant to your complaint. But again, no where in USPAP does such a method get banned.
In much of the property types I do there is no "good" way to do it. You have a wide range of values and other than proximity and recentness, the "similarity" of one mineral interest over another is often, at best, only broadly discernible. I can't see underground. That's why I tend to look at 30 or more sales when they are available. And I may simply take the mean as a metric as close as any other.
The differences between an 80 acre farm with a 40 year old house and barn is vast between one of 120 acres and a 10 year old home, but may be the "best" sale. Or is it the 60 acre farm with the 30 year old house? Or, perhaps the cost approach is the best way to value the subject? It is a judgment. And often when faced by these differences, it's not possible to single "one" sale out as the "most similar". You might determine the most proximate...but is that a meaningful metric really? or the most recent, again, in flat market conditions, that might be perfectly meaningless. It's a choice. And USPAP itself is ambivalent about some choices as it notes, as it says the "amount of detail required will vary with the significance of the information to the appraisal."
False accuracy is a big problem in this industry as most appraisers fail to accurately determine the actual "accuracy" that they are capable of. Few of us are "that good"...