I think that's a bit of a mis-read of the facts Goober (even though at face value they are as you describe). Personally, I wouldn't under estimate the difference made by AP McCoy in a finish. Barry Cash rode him to third when he went down by half a length to a Hardy Eustace who was at the top of his game, and a neck to Harchibald. You might argue that Cash was on board when he out battled War of Attrition to get a neck verdict in the Supreme, but they were both novices of equal standing. At the time he was taking on Hardy et al, he was in first seaon out of novice company, and the other two horses were probably entitled to be slightly better in terms of natural development anyway being closer to their peaks.
Leaving that aside, a few weeks later at Punchestown with McCoy in the plate the neck defeat to Harchibald had been turned around to a head victory. It is therefore quite possible that the horse remained essentially the same animal, putting in the same effort, but when margins are so tight, as they were in this case, McCoy was able to squeeze that bit more out that made the difference between the horse being considered gutsy, and being considered a valiant bridesmaid. I think we can over-state jockeyship, but at the apex where margins are fine this can make the difference. Its my best guess that Brave Inca probably put in a similar amount of effort in both runs, its just that McCoy's urgings were enough to get him to go to the bottom of an empty well, and find an extra quarter of a length in a fighting run in.
The next year of course was Inca's second open season, and I know they thought hard about going novice chasing. I'm sure Cantoris has said that AP's input although not decissive, was instrumental in their eventual decision to stay over hurdles. McCoy clearly thought he'd seen something in Inca and from then on he tended to win more of his fighting finishes than he lost.
I note also that it was Ruby Walsh who set up his defeat to Sublimity, with AP having to do a deal that meant him riding Straw Bear. What happened, (and the sections bear this out) is that Hardy and Inca essentially cut each others throats. Other horses fell or broke down when travelling well, whilst others just didn't turn up on the day. It was a very strange renewal, and one which I still think Sublimity inheritted rather than won.