But how can I be familiar with S3 without any data engineering work? Or maybe I should put it like this, what exactly does "familiar with S3" mean? Does it mean that I used it to store something (I mean even a non-programmer can do that), or that I should be able to manipulate (i/o) the store using Python with Boto (Again this can be done with a tutorial), or something else?

I believe that "something else" usually indicates some previous data engineering work though, so it's an egg and chicken problem.