I don't work for Google and i haven't interviewed with them. In our company (low level systems engineering) we ask similar question, with the following rationale:

I don't want to test if you can build systems, your resume already says so and there is but enough time to assess this properly anyway.

But, can you be bothered to try to solve problems outside of your comfort zone? Will you humor me as an interviewer for one hour with something that is maybe new to you?

If you rise to the challenge and attempt to solve these problems,i extrapolate to the systems engineering part.