I wouldn't consider NAP confirming a draw an active involvement in the
illegal action taken by AP. I'd rule GRV+FtMGS here.
Quoting Toby Elliott on his Policy Perspectives blog post on the M15 IPG
update
<
http://blogs.magicjudges.org/telliott/2014/07/14/m15-policy-changes/>:
It should only apply when one player performs a one-shot effect and the
other player gets involved in completing it (subsequently making a mistake).
//DLI