General domain knowledge. We do Scala and a little bit of Python here and there. You should know the difference to show you're well rounded. Senior devs sound have some experience in both types.

I have a follow up question, "What are the advantages of a dynamically typed language over a statically typed one?"

This one kinda exposes the "Java-zellot" side of programming. If you love Scala and you're applying for Scala position, you don't often think like this. Being able to think critically about the things that are harder in Scala, that would be easier in a language without strict type checking, is a another good way to gauge if people can think critically.