At the bottom of the first assignment, we have a note...
** Your assignment will most likely not be the same size as the instructor's solution. This information is provided because some students have turned in assignments that are far more complex than required. This information gives you an idea of how sophisticated your solution should be.
Perhaps we should put this note in a different spot.
The answer to your question 'Are these "hints" sort of like requirements?' is that they are not requirements. The Cattle Drive focuses on making your code simple and readable.
You should do the best you can and then turn it in. If you just say, "It runs, good enough", you will be more likely to get it back from the nitpicker with more suggestions on how you might improve your code rather than the instructor's solution. The deal is that you can only proceed to the next assignment after you receive the instructor's solution to the current assignment.
However, your solution does not need to exactly match the instructor's solution in order for you to "pass" the assignment. If your solution is 60 lines long and the instructor's solution is 5 lines long, then the "hint" will indicate that you have some work ahead of you.