IMO Jimmy FWIW and off the top of me head-
"Reaction" is speed.
When one is playing, the speed (reaction to what their mind "hears") happens.
The technique and results of the "speed" is based on how much the player practiced and how.
The theory, learning licks, picking/playing techniques, scales and everything else one may practice are only means to help one gain the ability to "talk" or play what they hear (without much thinking) which also results in their own unique style. ( "second nature" comes to mind.)
To me that is the coolest thing about being a musician. Others may try to sound like you but nobody can.
That is why Carlos could use my equipment and all listening would know it was Carlos playing.
Not unlike training for sports. The quick "natural" reaction of moves they may make are possible
when their training and natural ability take place without the loss of time taken by "over thinking" it.
Not sure that makes sense to others but that's how I see it...or probably the best I can do putting it into words.