I would guess that this is a simple misunderstanding, and an attempt at an actual "theft" isn't being accurately reported, but I would agree with you - if your role at a company ends, your credentials are usually revoked to prevent any further access and my guess would be that, as soon as the decision to stop any more work on Batgirl was made, everyone involved who initially had access to "the server" all had their login's revoked.
However the "it was done to prevent theft" storyline is one which adds a little mystery - maybe it stemmed from someone overhearing a chat between folks effectively saying "this is crap, we spent ages on this, sod it should just take the film, it's ours" as they were blowing off steam etc rather than as a genuine threat to steal it.