Seems to me that’s the simplest and most intuitive point of view. Can you imagine publishing a question and then owning the copyright to every answer to it someone writes!?
There is a difference between "Questions" and "test questions with a known specific solution". One could argue (I would not) that the solution to a test question is an integral part of the question and therefor if the one can be protected by copyright, so can the other".
While that would apply to simple maths questions — 16x16 is always 256 — I don’t see that applying to HackerRank programming challenges, where the challenges (last time I used it) are essentially “produce correct output from this mostly-secret input”, and they don’t even mind which language you use to do this, never mind what variable names you use.