Using computers, it has been found that there is a limit of some 21-23 moves to solve any configuration of the cube, so in theory if you knew all the billions++ possible states, you could just do the required 2x steps as fast as possible and then work on motor skills from there, but of course reality is that you can't memorize them all so it is some kind of tradeoff between knowing a lot of patterns and applying the shortest solution you know to take it closer to solved.
All the people solving in seconds aren't even using the same methods, so some will be better at planning while they look at the cube before the start, some will have faster motor skills.
Like you said, none of these folks are deriving God's Algorithm[0] in their heads in the planning stages. I haven't been in the game for a while but I'm pretty sure people are all still doing CFOP[1] but getting better at lookahead, execution, and some of the advanced tricks like x-cross[2], and a bunch of gnarly last-layer tricks[3]. Some of which include memorizing thousands of algorithms.
The diameter of the cube group is 20, but speedcubers go for natural/memorized sequences of moves they can execute extremely quickly ("fingertrick") over technically shorter but awkward move sequences that require grip adjustments, have hard to visualize side effects, and so on.
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Using computers, it has been found that there is a limit of some 21-23 moves to solve any configuration of the cube, so in theory if you knew all the billions++ possible states, you could just do the required 2x steps as fast as possible and then work on motor skills from there, but of course reality is that you can't memorize them all so it is some kind of tradeoff between knowing a lot of patterns and applying the shortest solution you know to take it closer to solved.
All the people solving in seconds aren't even using the same methods, so some will be better at planning while they look at the cube before the start, some will have faster motor skills.
Like you said, none of these folks are deriving God's Algorithm[0] in their heads in the planning stages. I haven't been in the game for a while but I'm pretty sure people are all still doing CFOP[1] but getting better at lookahead, execution, and some of the advanced tricks like x-cross[2], and a bunch of gnarly last-layer tricks[3]. Some of which include memorizing thousands of algorithms.
[0] https://en.wikipedia.org/wiki/God%27s_algorithm
[1] https://jperm.net/3x3/cfop
[2] https://jperm.net/3x3/cfop/cross
[3] https://jperm.net/3x3/cfop/ll
The diameter of the cube group is 20, but speedcubers go for natural/memorized sequences of moves they can execute extremely quickly ("fingertrick") over technically shorter but awkward move sequences that require grip adjustments, have hard to visualize side effects, and so on.
Total cube positions is 43,252,003,274,489,856,000.
And any position can be solved in as few as 20 moves, aka “God’s number”
https://www.cube20.org/
"in as few as 20 moves" is wrong, it's stating a minimum with an unbounded maximum.
The site states "20 moves or less" which is stating a maximum.