It also helps because software is one of the rare engineering fields where code is non-destrictive and can be changed after the fact.

The carpenters trick of measure many times, cut once, can instead just be cut and re-size if wrong size, which can often be quicker.

Asking how long they want me to spend on it also let's me know how solid it needs to be engineered. Is it something that needs doing right then first time, or do we just want something rough that we can refine later with feedback.