Personally, I have to put my money with the Green Dragon blog: the old-school Renaissance ALREADY is excluding certain elements of the D&D back-catalog and focusing on others.
Where is the BECMI/Rule Cyclopedia Retro-clone? There isn't one. There are two Mentzer and B/X clones, but none that have elf-as-class, law/neu/chaos alignments or maxed leveling at 36.
Where is the Second Edition Retro-clone? Oh, right. "Old school" players would rather forget second edition even happened. AD&D 1e gets all sorts of fond memories and even its own clone (OSRIC) but 2e is regarded as an abomination; too recent to be "old school", to archaic to be "new school."
Currently, the "old school" Renaissance mostly consists of people who gamed during the late 70's and early 80's trying to recapture the games of that era. The mood, tone, style, and even artwork and typesetting evokes the feeling of those pre-1984 gaming, and lets everything else go hang. It comes off sounding like the "rose-tinted glasses of nostalgia" because it ignores (willfully or otherwise) any and all innovations for the past 15 years.
Well, it tries. I wonder how many people (to use the blog's example) re-rolls hp every day? How many "borrow" spells and classes and races from later editions? Heck, nearly every retro-clone has an option to "ascend" AC, a D&D innovation that didn't see official production until 2000.
Now, if you enjoy that sort of game, more power to you. I reject the notion that OD&D, 1e, or a derived retro-clone is any more "pure" than 2e, Pathfinder, or 4e.