While I agree with the OP, some questions are just terrible. Some do not imply context. Some have too many correct answers. Ask someone "Who are you?" without providing verbal context to the question and you will probably get their name. But ask them that same question in a situation where you know they know you know their name and you are likely to get a wide range of responses - all correct but most are unlikely to satisfy the intent of your question.

The size of said bag was never defined. Use your imagination. In my imagination it is a magical bag of endless holding.