It didn't result in a goal?
Also on the FA site the rule stipulates that it is only handball if the player "gains possession/control of the ball"
and then scores/creates a goalscoring opportunity. Since Silva did not gain possession/control of the ball, the rule regarding the creation of a goalscoring opportunity doesn't seem to come into it.
The rule regarding accidental handball seems to only be activated in the instance of a goal actually being scored. Since a goal was not scored, the accidental handball rule likewise doesn't seem to apply.
In fact the only guideline that seems relevant is the one regarding deflections off another player. As far as I know though that isn't the guideline VAR is citing in choosing not to call a penalty (maybe I'm wrong).