With what Piggybird said, remember, it was stated at first that you shouldn't study in a bubble.

Sticking to one resource isn't useful in any skill you want to achieve. For example, if you want to learn Spanish and you just buy a single Spanish learning book, you will not go very far. Some intricate details that is forgotten to mention or isn't apparent to the author means that you also miss that point. You have to gather information from multiple sources, like how you would also watch Michael Hampton or Proko for example; you want to hear how native speakers speak, like how you would watch how master artist draw; you want to speak and make an output, like how you would doodle and experiment outside the course...

Of course, if you are casually learning it, sticking to one resource is fine. There's nothing wrong with being casual, some people just want to enhance their world views, some people just trying to draw without mastery level, or you may be just a bored guy looking to spend time. I feel like you are not trying to do this casually, as I just wanted to tell this to whoever may need it :P

You already stated that you will abide by the rules of the course and don't mix-and-match with other courses, so that is perfect.

Have fun in your journey!