This theory has never made any sense because it isn't how target specs work. Developers aren't running numbers on what is in the devkits
Here is an example of target specs. This was leaked in April 2004, over a year before the 360 was even announced and was certainly available to developers a few months before that
More details in narrative form leaked a short time later:
https://web.archive.org/web/20040705082242/http://forums.xbox-scene.com/index.php?showtopic=231928
Sure, the clock speed changed the RAM amount but beyond that everything was well known and communicated to developers
Something like a fantasy gcn->navi FLOPS conversion would make more sense in a document like the one below explaining
dev kit differences, not t
arget specs. Note: the new dev kits described within (with a wildly different architecture) weren't delivered until like August or September 2005 (and the clockspeed changed again). The console launched in November 2005
(many people here will probably remember this as it circulated widely ahead of 360 announcement)
They were working on completely different hardware but it doesnt change that everyone knew the 360 specs
You can see the same with the Orbis/Durango leaks, though the timeline was a little later with those. The target specs were very detailed and only clocks and ram ever changed
"Insiders" are being vague only because they want/need to be, or they haven't really seen the target specs and have 2nd hand info. There isn't a scenario where someone has the target specs and is confused because the devkits are old (other than minor changes)