Nxg3 is brilliant even though it’s basically theory
They made revisions to what gets called "brilliant" several months ago.
I don't believe that it checks to see if the move is still within what gets considered as known theory but I'm not sure.
But if you look at the database here, the position after 6..Nxe4 comes up in 28 games. In none of those games did white respond Ke1. White played Kg1, Ke3 or Kf1.
That happened in your game, taking it out of theory and into the range of brilliance.
Nxg3 is brilliant even though it’s basically theory