[B. Dudley]

The forend is the final piece of the puzzle in a way. But the gun should be tight with the forend off.

The only thing the forend has to do with anything is maintain a tight feel when the gun is opened up.

Your tightness with the forend off is all done with the hook and the locking lug/bolt.

True, that what is really important is if the gun is tight In shooting position (with forend on), but, the forend is not considered an integral part of the "bolting mechanism" per say.