Debugging is a skill that will definitely be used on the job, and this is a stripped-down example of something that you'll definitely encounter while working in JavaScript (or any language with mutable closures).

How would you ask about this issue in interviews?

This isn't really a tricky question who understands how JS works. If a person has not experienced this situation of a function call (closures) within a loop, I'd suspect he has not much practical experience.

It's much more difficult to understand this theoretically than when encounter this while you code.