Well, amigo...I understand your points. But, I don't agree with them..completely.
I am happy to let you give Frayling the benefit of the doubt---but, I won't.
Long story there and it involves personal exchanges and whatnot, not worth going into here.
At the risk of launching into the realm of the way off topic.....
I think, having studied authentic "Western" period clothing a great deal, that there were a lot more Spaghetti Westerns that were closer to RIGHT than there were American Westerns (especially of the late 50's and into the 1960's). Of course, not all of them were..but, some were.
I, and a few of my Old West historian buddies (Bob Boze Bell and Drew Gomber, among them), feel that most of the time the sets and costumes in the Italian Westerns were way more authentic than say the typical John Wayne Western made in the same era. Of course, this sort of blanket statement doesn't entirely apply to all films (Italian or American)--and it especially doesn't apply to films made by folks like Fidani, Crea, and so forth! ha ha!
But, the main point I would like to make here is that NOBODY gets it 100% "correct" when it comes to locations, costumes, or sets. The closest I have seen, so far, would be the movie TOMBSTONE (and there are a few errors there, too).
One of the worst is the highly regarded American film TRUE GRIT.
They are supposed to be in the Oklahoma territory in that film and all around them are the great Rocky Mountains of Colorado!! There are no such mountains in Oklahoma...period.
And what about John Ford making Monument Valley out to be Texas? That aint right, either! Well, OK..some small part of the Big Bend territory might pass...but, overall...no.
So, personally, I think the Italians and the Spanish did as good, if not better, at showing just as much authenticity as many American filmmakers ever did.
And by that token, they deserve as much respect.
I feel Frayling (whom I have heard is distancing himself from the whole Italian Western thing, now, and is actually growing tired of discussing Leone!!) did the sub-genre a huge dis-service by his back-handed remark which--as you have pointed out, amigo--lends itself to the interpretation that the Italians just didn't know what they were doing when they were making Westerns.
Many of them did.