Perhaps. But if it's so obvious, won't it be an open-and-shut case?
It should be a big deal. We really don't want drug companies being able to skip to a position on effectiveness that is convenient for marketing reasons.
It's not like Pfizer are short of cash to defend themselves.
If it starts to become a money pit, then it means there's a knotty issue to be solved, and that's important to know about.
It really doesn't matter if it's obvious / open and shut. It takes up time, energy, and erodes public confidence in basic science. This will cost the state, the company, and possible federal money to process, all for bullshit claims and Ken Paxton's not-based-in-reality ego.
Public confidence will be shaken more by an attempt to prevent the case being heard. If they win — assuming for all the right reasons — then it's a boost all around.
If they loose, then... well, you're right that it'll be a bad day for lots of people. But could anyone really argue it would have been better to not know? I'd be shocked if anyone did.
Like that time he sued to overturn other states' elections.