Yeah you can write the code yourself. You can also write in c or even assembly if you really want to make it as unambiguous as possible, it'll just take more time. Some people like to code in Python though because they can write faster with it even if a lot of implementation details and choices are hidden from them because they don't care about those details.
Spec driven development in my view is just another step, albeit a big one, on the level of abstraction between assembly and python. Like python it has its places and has places where it should never be used for safety and performance reasons.