The article doesn't seem to say this specifically, but my take at defining "gridification", in the sense of "why is this term in particular used to refer to the thing they are talking about". The article says "Gridification is when a human performance is treated as error in need of correction and turned into a machine-perfect representation of itself" but they could have used "blorficoration" for this; why "grid"?

Griddification is trying to take each note and align it to a grid, the two axes being time and pitch. All notes (spoken or sung or struck) start aligned and are tonally compatible. In that sense it is like the grid you see on a piano roll describing music. Basically a de-jittered midi-style reduction of the actual music being player.