That’s it.
The individual who has a breakthrough often feels compelled to call it a “system” and start telling others about it.
The great advice someone has is just what worked for them. It will probably work for others, especially if it repeats common advice, but it won’t work for everyone.
My take is that there are probably multiple systems out there than can help you achieve mastery, but it depends on your personality, life circumstances, etc. Just like there ten thousand paths up the mountain. It is a good idea to try out a couple and find the one that works for you. Then if you get to the point where you master your target skill and it is your turn to spread the gospel of "the way", it is good to keep in mind why it worked for you.
There’s also a causal bias here.
If I practice guitar for 6 hours a day (like John Petrucci in his teenage years) while always wearing an orange hat, I’ll get pretty damn good at the guitar in a few years. I can then spread the word to everyone that the best way to learn the guitar is to always wear an orange hat.
As with the dangers of ‘productivity porn’, ultimately what matters most is putting in the hours.