From the CFL Rulebook
• When a ball carrier is on the ground and, in the judgment of the official, is not
attempting to advance the ball, the official shall immediately declare the ball
dead.
So if a Player goes down on their own then are they not to be ruled Down ? Its the Officials call but if it was me and I saw a player going down on their own it suggests they are not trying to advance the ball !
I do agree that if no whistle the play is not dead but the argument the other side is making is the Offical should have ruled it dead because he gave himself up, as for AC a few years back he dove head first but lost the ball when he hit the ground ( so before the whisle )