Obviously, the above is exaggerated, but the point remains that any answer or non-answer by the students can be interpreted as a lack of math skills and evidenc

Obviously, the above is exaggerated, but the point remains that any answer or non-answer by the students can be interpreted as a lack of math skills and evidence of poor critical thinking. That point remains wrong. You can treat the question as a Fermi problem, but when you do that, it's because you realize and acknowledge that there isn't enough information in the problem to complete it by other means.