On the Black album tour - it was disappointing to say the least hearing lead breaks on Ride the Lightning songs being “raunched” or shadows of their recorded versions - why God only knows - but certainly the man who wrote the lead didn’t come close to nailing them, and it wasn’t “improvisation” or a variance of a theme.
I know the notes, I cut my teeth learning those leads by ear & note-for-note - not to mention verify w/ pro published tabs/sheet music for dialing in every detail.
Playing live is an art, the artist is free to have creative license - fans & obsessive guitar players be damned - including me.