Flatbed scanners are great when you just cannot seem to get a page scanned through the ADF without slipping causing bad scans OR because the cover is cardboard and simply cannot be used on an ADF system (I scan books as well as mags which is where that comment comes from).
I think you misunderstand although I can only comment regarding my website and not Retromags. kitsunebi has spelt out the standards here at Retromags and they are not that onerous. Try looking at OoPA if you want to see quality nitpicking of the Jedi magnitude. Meanwhile, for OGM I take a similar but slightly more relaxed view in that as long as:
They aren't raw scans, e.g, they have been cropped
Scanned more than 200DPI preferably
preferably received NOT resized but that is desirable and not mandatory
.... then I am okay with that. Blemishes on the pages I am okay with as I'd rather get the magazines out there for someone else to contribute by editing. There are too few scanning members in our "scene" so I adopt that mantra because if a scanning member quits or becomes incapacitated and they never got around to scanning their collection because they were too busy doing nitpicky editing work then that's a tragedy for the preservation scene, especially if they are the only one with previously unscanned mags.
The big problem with book scanners is that by having the lens so far away from the printed page it layers in the typical blurring you get as a result of that. With images that isn't really a problem which is why camera's are good for that type of thing. Text of the size on a typical magazine on the other hand really doesn't lend well to being photographed. Too many factors come into play. Archive.org is probably THE WORST place for quality scans. They use book scanners in a major way as they use them to photograph Library of Congress and other material etc which obviously cannot be destroyed to get a digital copy. You can see it in their scans which can be described as mediocre at best. The best scans they have over there were ripped off sites like our wholesale by their resident wanker Jason "Sketch the Cow" Scott without any acknowledgement of where he got them at all. They are pretty much a swear word around here.