Do you have a source for that Bobby Fischer anecdote? I’ve read several biographies, and I’ve never heard it mentioned that he had trouble memorizing openings. There were, however, quite a few stories that suggest he had perfect recall.
Here is one such interview: https://youtu.be/7EuxVOgrEig
From https://en.wikipedia.org/wiki/Bobby_Fischer#Opening_theory
> "He employs a limited range of openings. Of course, this is not a sign of Fischer's limited creativity, since he compensates for this by a very profound and sound knowledge of the variations he favours [sic]." Plisetsky & Voronkov 2005, p. 270.
> Fischer was renowned for his opening preparation and made numerous contributions to chess opening theory
He promoted (not invented) Fischerrandom / Chess960 because he felt that memorizing ever-long opening sequences was boring and ruined the game, and that would be soon dominated by computers with their far-superior memory.
Fischer was, despite being, at one point, the greatest chess player in the world, and on people's all-time greatest lists, predictable in his use of openings, as you know since this is widely documented and you're well-read on him. Your quote even admits this.
So I'm not sure what you are exactly disagreeing with that I said. Maybe the source of disagreement is that I unintentionally gave the impression that he has a bad memory, or a bad opening game. As he was one of the greatest chess players, this was clearly not true. Rather, the idea was that he had a notable disdain and discouragement from memorizing learning opening game theory. He was never able to master a very large number of openings... This was a notable feature of him as a player.
Perhaps he could have, but that would be speculation. I think he just wasn't as good at it as the other top players.