“ Stockfish move calculator is almost unbeatable”
Not almost. It is. The ELO rating of Stockfish is 3500+. The best human, Carlsen is somewhere around 2850. Stockfish is light years ahead in terms of ability and even running on an average laptop will beat Magnus 99 times out of 100.
“will beat Magnus 99 times out of 100’
I guess that does make it ‘almost’
The ELO ratings of humans and machines aren’t really comparable, since they have no common base. Also, even if Carlsen only beat Stockfish 1 time out of 100 (which is very likely too low), there would probably also be a dozen or so draws.