That stood out to me as well in his inking class. I think because he has a lot of experience with drawing, he has the flexibility to lay down general lines and shapes as guides and then kind of come up with an inked drawing on the fly. Similar to a musician that has played an instrument for so long that they are able to have an impromptu jam session with just a random group of people. We're just in different places along the drawing spectrum. If we'd like to get to a point similar to where he is at, I think it helps to go slightly outside of our comfort zone and maybe not make as refined a sketch as we're used to and see what the end result is.
With that being said, I'm sure there are many artists that continue to use refined sketches because for their style it results in a better end product. I kind of land in that group, but I have been wanting to evolve my approach and watching Jake sketch/draw/ink gave me some ideas to try. The thing that really stood out to me was that he said that part of the fun was discovering the drawing when going from a rough sketch to the inking process (at least that's what I think he said). And I wanted to know what that "fun" was, so I tried it with my last two Inktober sketches. While my sketches where definitely not as loose as his, it was looser than what I was used to. And I was pleasantly surprised when things emerged from the sketches that I liked (and of course there were things that I made mistakes on, but I had no choice but to move on). It was kind of nerve-wracking, to be honest. But because of that, I almost felt like my brain tried to kick itself up a notch, and I found myself thinking a bit more in depth about how I approached the shapes and lines.
I'm sure the more inking practice we get under our belt, the more comfortable we'll get. Sorry for the novel.
*side note: during the whole sketching/inking process, I continually felt the urge to hit Ctrl+Z, or lasso and resize, lol.