Any Wharton grads to clarify something?

So, i've taken the introduction to financial accounting & more introduction to financial accounting courses taught by Brian Bushee(great professor) who is a professor at Wharton and read the syllabus related to the accounting courses held at Wharton and it mentioned the fact that textbooks are complementary to the courses and are no means to replace them.

My question is what is the main difference between the courses and the books mentioned in the syllabus? What topics do the professors cover that the books don't?

+SB for answers

Thank you.