As @talves has already said, you should speak to your professor about it.
It’s likely the assignment requirements have a minor error, or are simply outdated.
Netlify did originally serve customer sites under .netlify.com, but moved to use .netlify.app
You can read more about it here, (and provide your professor this link):
https://answers.netlify.com/t/deprecating-automatic-com-redirects/115442