If some guy had a good employment history, maybe a GitHub with some examples of their skills and described an algorithm to me... Why would I doubt their ability to write it in code?
I wouldn't take that for granted. It's easy to gloss over details and edge cases when talking through an algorithm and it's not apparent until you actually write the code. Similar things happen when discussing things in meetings vs writing a formal document. I've interviewed plenty of people that were able to quickly come up with algorithms to solve a problem but really struggled to translate them into code.