Interview at Microsoft Serbia, around 2018-2019, for a general Junior Software Engineer position.

My expertise was in Machine Learning (this was way before LLMs and the current AI craze).

The first guy knew what ML was, but advised me to round up my knowledge with low level coding, cause ML is too abstract and isn't very useful.

2nd and 3rd guy gave me a mix of stupid brain teasers and high school math, coupled with questions about obscure C++ libraries (despite me clearly saying I've only done C++ back in high school and don't really ever use it).

The 4th guy, however, was the actual bizarre part. He was completely introverted or something, kept looking at the desk and eventually whispered to me:

HIM: Write an API for a book with chapters. It should be able to flip to the next chapter and flip to the next page.

ME: Sure, no problem, that's trivial. By the way, when the user is at the last page of a chapter and calls nextPage, should it give null or skip to the first page of the next chapter? What if it's the last chapter/page and the user is calling nextChapter/nextPage? Give null? Throw error?

HIM: Write an API to flip the pages and chapters of a book.

ME: Yes, I understand. But if I'm at the last page should it give null?

HIM: The book has pages and chapters. Your API should be able to navigate to the next page and next chapter.

ME: So you keep repeating the question over and over again, and not answering my question.

HIM: I don't know how I can say this any clearer, the book has chapters and pages and your API should navigate to the next chapter and page.

ME: You know, I'm just gonna write this with the null thing in it and we'll go over it line by line.

After a minute or so, I go through the lines and we get to the null part, I look at him while I'm explaining the line and his face shows no pattern recognition to my question. After I finish going through the code, he just picks up his stuff and says "Thank you for your time".

So was this a behavioral interview in disguise or what even happened there?