I can see both sides of this. I really want different part numbers for the same reason you do.

However we deal with a lot of regulated products and to just open a case at one of the Government Paper-Pusher Regulators will cost us $5,000 to just change the part number. We are a small company and $5k hurts.

I'm sure it does and you have my sympathies, but your situation would not be a reason to let Texas freakin' Instruments off the hook. They're not exactly "a small company", and I wouldn't be surprised if the $5k would have been cheaper than dealing with the response to this, so this just comes across as incompetence on their end.

... How do the "paper-pusher regulators" feel about getting a completely different part unannounced? I would guess unhappy, tbh. Like based on the thread it's not trivial changes.