Intuit has a pretty broad financial software portfolio, not just a tax company.
Also, yes the actual arithmetic at the end should be handled by deterministic code. I doubt anyone, including Intuit, thinks otherwise. But there's a ton of uses for LLMs before you get to 2+2 = 4, explaining concepts, document extraction, understanding the full financial picture, etc.
Kind of feels like you're criticizing a cartoonish idea of AI's place in their products.