If you're tweaking your lesson plans to make concepts more clear, that benefits all your students as well. For the most part, you're getting additional income

If you're tweaking your lesson plans to make concepts more clear, that benefits all your students as well. For the most part, you're getting additional income for little extra work, and what work you do to improve your side job comes back to improve your day job as well. If you're spending hours struggling with a system that is difficult to set up / get it to pay out / otherwise distract from teaching, then sure. But I haven't used the system so I couldn't say whether or not issues like this are occurring (and it certainly sounds like it's working for the teacher in question).