[d--b]

The question is: what mistake should the developer not do?

A bad developer will not implement properly the separation between infrastructure code and business code.

A bad developer does not care about readability, so the code will be laden with functions that have side effects, and things of that nature.

A bad developer does not comment their code in a meaningful way.

None of these are easy to find out in an interview. It turns out that questions about algorithms are good proxies to find people who are interested and proficient in computer science.

Sure you will miss some good developers that aren't good at algorithms, but there is a better chance that you do not hire bad candidates.

[groomed]

You mentioned all three things that algo-strong dev will also do. Because there is no correlation