This is a bad take. Current chess lines rely on the exact position of pieces. When you shuffle the starting position, all theory that relies on exact position falls apart. Only high-level ideas carry over when a position isn't exactly the same as the one you studied.
You're implying that 3 moves (12 minus 9) corresponds to ~960 less lines to memorize. Sure, that might be applicable when tacking moves on to the end of a line you already have memorized (though I would certainly argue 3 moves would result in far less than 960 new lines, maybe 20 lines max). But when you're moving these 3 new moves to the beginning instead of the end, as you must in Fischer Random, then you do see true combinatorial explosion. You'd have to study far far more to have theory developed for every starting position.
No, it's a decent take. The grandparent probably meant moves per side, so 6 fewer plies. Memorizing opening lines in Chess960 is certainly possible thanks to chess programs giving you an idea of why these moves were chosen without learning all the intricacies of the given opening position, it does give you a pretty big advantage, and the theory does not "fall apart."
> The random setup makes gaining an advantage through the memorization of openings impracticable; players instead must rely more on their skill and creativity over the board.
It's not just the 960 unique starting positions, but then each of those if given enough analysis probably has 2-4 optimal 1st moves for white, plus 3-5 optimal 1st move responses for black. That's roughly 5,760 - 19,200 optimal 1st move pairs, which is a lot to memorize to just get you to the 2nd move.
At the GM level, a traditional opening is anywhere from 5 - 15 moves long before you might see a non-trival expectation of deviating from explored lines, so memorizing 960 openings to any reasonable level of depth quickly becomes highly impractical.
You're implying that 3 moves (12 minus 9) corresponds to ~960 less lines to memorize. Sure, that might be applicable when tacking moves on to the end of a line you already have memorized (though I would certainly argue 3 moves would result in far less than 960 new lines, maybe 20 lines max). But when you're moving these 3 new moves to the beginning instead of the end, as you must in Fischer Random, then you do see true combinatorial explosion. You'd have to study far far more to have theory developed for every starting position.