I genuinely don't know. I just don't want to look biased.
The offside rules are pretty clear (page 94 of IFAB's Laws of the game 2017/2018).
A player is offside if the ball, passed by a teammate, has "rebounded or been deflected... by an opponent"
A player is NOT offside if he receives the ball, initially passed by a teammate, "from an opponent who deliberately plays the ball"
So, if we consider Alex Sandro's (double) touch unintentional, it is offside. If we consider it deliberate, it is not offside.
This is why it was such a tricky decision and it took so much time. Pioli argues that the double touch was deliberate, so it's not offside. The VAR considered it involuntary, and that's why he ruled it offside.
