Lanefan
Victoria Rules
So by your definition someone using only the original gray box all these years isn't running a FR game?Which means you are not actually using the realms, you just use a 3rd party map for your games.
That seems a bit over the top.
This gets back to the core theme of a major thread in here from last fall to do with canon and lore and so forth, where some people (not me!) argued that pretty much any DM-induced change to established canon in a setting invalidated the game as being a <whatever setting> game.
But here, the issue is timing. If, for example, I'd started a campaign in 1990 or so (whenever the gray box came out) and used the info as written then...and then ignored all the additional "official" material that came later because events and changes within the campaign took precedence...I'd say I'm still running a FR game even though the fictional history would very likely by now be so widely divergent as to be almost unrecognizable.
Someone who started a campaign using the 3e FR sourcebook and then let things develop on their own is also just as much running a FR game.
In short: once the campaign starts, its own events trump and supercede anything "official". If a PC party manages to burn Neverwinter to the ground during a campaign and two months later an official supplement comes out detailing how Neverwinter has become a major military force all of a sudden, well guess what? Supplement ignored.

Lanefan