I completely agree with your application of learning. In fact I often encourage it in my videos. While I think this is the best way to establish lasting knowledge, not everyone prefers it. Especially for new users who often lack the confidence to do their own projects. Early on it’s common to need a bit of hand-holding until the confidence is built up.
Also with exercises that are designed to be systematic and objectively graded as much as possible, it helps to have a standardized goal with specific guidelines. If this exercises was “sculpt anything you want” then the grading would be the wild west, degrading its value. Also we’d only ever need to have one sculpting exercise because that would encompass all possible topics.
For artists like yourself exercises could be irrelevant, being based on specific guidelines. Instead of submitting your realistic shark to the exercise, I recommend submitting to the gallery and linking to the course to make the connection.
In the end the ultimate goal is that you’re learning regardless of if you’re passing exercises or not. Clearly you’ve learned how to sculpt well because your shark looks great! As lame as it probably seems to you, it technically doesn’t meet the exercise requirements. Don’t mistake that for a negative reflection of your work.