So that demo is admittedly from quite a long time ago, so it's a little loose and due for an update with the overhaul - but your conclusions are still largely accurate. The thing to keep in mind most of all is that the goal here is not to draw all of the fur in your reference image. The goal is to convey the impression that this animal is intended to be furry, and that has a far lower bar to achieve. All we need to do is provide enough fur to inform the viewer's mind what they're looking at, and it'll fill the rest. And so from there, we try and find where we can add that fur that will require fewer actual marks, but will convey the strongest impression.

First we can achieve that most of all at the silhouette, because that's what the viewer's eye catches before anything else, and thus has the greatest impact. Purposefully designed tufts - each one given its own separate effort, rather than trying to repeat the same motif on autopilot.

From there, if we need a little more, we can look at the areas where there might traditionally be some more prominent form shading that would give us an excuse to add some texture - because texture can create gradients of density, which can given the tools we're using in this course (full black with the fineliners, full white from the paper, and nothing in between) be a great opportunity to slip in some texture. Just keep in mind that the goal here is not to convey the form shading - it's to convey the texture. It's easy to get roped up into the mindset that we want to add lots of form shading (in pursuit of decoration), and just end up scribbling the gradients, instead of focusing on the gradient itself and each individually designed cast shadow shape.

Of course, given that texture of this sort is made up of the shadows cast by our textural forms, it helps to focus on the fur in groupings of strands, as this gives us something with a little more volume, and thus something more substantial from which to derive our cast shadows.

Lastly - remember that the cast shadows we draw are not copied from the reference, but rather are drawn based on our understanding of how the textural form we're introducing to the drawing relates to the surfaces and forms around it. So we look at our reference to understand the nature of the form, as it exists in 3D space, and we use that understanding to design our cast shadow shapes. We do not identify cast shadow shapes in our reference and transfer them directly, as this is an action of looking at a 2D element in the photo, and capturing it as a 2D element on the drawing, without ever having understood it in 3D.

Hope that helps!