:History: Industry threatening to leave if social change takes effect
What's going on when a for-profit company makes a threat?

The same thing that is happening when does anything. It is trying to increase its profits, relative to what would happen if it didn't do the thing.

In this case, it's trying to influence policy to protect its profits. It has decided that issuing the threat gives their profits a better chance than not issuing the threat. That probably means that they believe that their profits will be lower with the new policy than without it.

The thing it's threatening is, in a sense, neither here nor there: the threat itself is the action.

Should the policy that a company opposes, get implemented, then the company then has a choice, to stay or to go, and the decision criterion will be: will them staying result in higher or in lower profits than them staying. That's a completely different issue to the thing they issued the threat over, and the threat doesn't tell us anything useful about it.

And companies are often wrong about the impacts of policy anyway.  In summary, treat their statements on policy with a lot of scepticism.