While this could help with the mechanical calculations and preparation of returns, the wider point about ‘verbosity and ambiguity of human language’ can’t be nearly so easily dealt with outside the simplest cases, and would likely make the tax code /harder/ for people concerned to interpret and reason about, which is probably the opposite of the desired result.

Firstly the actual text of the law must be as legislated.

Secondly, law and most certainly tax law is necessarily nuanced in interpretation and the consequences for taxpayers and the government are material (to use a relatively simple and well-known British case, a machine-executable model would be unhelpful in determining whether Jaffa Cakes should be taxed for VAT as biscuits, or exempt as cakes. Then ask about chocolate chip cookies (zero rated) vs chocolate digestives (taxed!)). Stuff like this and more is argued about all the time.