>So, stapling them wouldn't really make any difference
>to them.

Sorry wrong answer, The studio does not staple,The 
Cels Dealer does.

If the dealer gets a bunch of cels from the studio expect
the cels to be in a big mess and the oversized cels
roled into a tube :-( Sad but ture.

As you said once the  studio is finished with the cels
they normally don't care what condition they are in and
the cel collector is and last person in their mind.

Stephen


* side note, some studios have bagged cels in the past,
This is normally for some event.