A few years ago I was involved in a discussion in an old motorbike club (the word retro wasn't in common usage back then) when the club was formed the cutoff date was 1975. The idea being it was a club for people who liked old cheap two stroke bikes, not expensive "classic" or "vintage" bikes. One member argued the the cutoff should remain static. Arguing against that several members thought that the cutoff should always be ten years prior to the current date. Otherwise the club would rapidly turn into one of those snotty "classic" or "vinatge" clubs as the bikes became rarer and more expensive. What happened was that the two factions formed their own clubs, neither would agree to the other using the original name so two entirely new clubs were created and then chased the members of the original club. Only to discover as the dust settled that the membership were sick of the infighting an there was nobody left.
As language evolves so does technology. In ten years time people will consider today's high tech marvels as retro. Even today a 2004 full susser seems rather quaint. What happens then? Do we end up having loads of forums that cater for different factions? Those that prefer the "vintage" era? Those that prefer the "classic" period. Those that prefer the "mid school" period? Continue until the distinctions create groups so small there is no discussion? Or do we all learn to live with each others' interpretations of the concept of retro and live as a one big happy family.
You need to remember that any group, club or forum exists because of it's founders, but continues to exist because of it's members. If there are members who want to see bikes built after some arbitary cutoff date then why not let them have their fun?
And no, I've no bloody idea what the terms in quotation marks mean.