Yes, that's an interview brain teaser of the exact variety Google and others have found doesn't indicate much in the way of actual job capability/fit. As someone else in the thread pointed out, anyone can look up the methodology for answering these types of questions in about a minute, and be able to tackle all of the variants easily with little actual thinking.
I agree that product managers need the ability to break down big problems (or requirements/client requests/company direction) into manageable pieces for their team to work on. However, there are better ways to gauge this ability, such as...
- Ask directly for an example of how they have taken a big problem or assignment and broken it down in the past
- Give them a real-world big problem you've had recently and ask them how they would break it up into team tasks/user stories/whatever you use
- Ask them to explain their methodology for determining how long something will take to build or test (ex. some people love planning poker, other people love logarithmic buckets, other people base estimates on experience, and others do something completely different)
Basically you'll get a lot more value out of interviews if you ask directly for experience or process they'll be using rather than trying to back into a skill estimate using a brain game.
