I don’t understand people who think like this.
knowledge of algorithms means nothing. No one in their right mind would ever have to implement an algorithm at any point in their career. Any developer worth their salt will use a library which already implements t and it’s guaranteed to have no bugs.
Only a very junior person would even attempt to write one. Reinventing the wheel is a big thing in software development. One can hide after other big words like engineering etc, but the reality remains that there is no need to implement one. If you do it, you've just proven you’re the same level as a junior person.
What are we left with? A whiteboard test with absolutely zero value, supervised by a person such as this one, who sounds bored and frankly does not show any enthusiasm. The best developers are those who put their name on something, you can find them in the community contributing, not some Google wannabe no one ever heard of of, with zero contributions to anything and the attitude of some who should not be in charge of hiring others.