It looks amazing but I feel like some of the texture was mistaken for shadow

As you improve in your knowledge of anatomy/figure drawing, your boxmen will also improve. However, the exercise isn't necessarily supposed to look good. It is intended to be a way to get your pencil moving, without stressing out about the result. When I posted my assignments for this course, I tried to make what I showed publicly meet some minimum threshold for quality (which was, by the way, unnecessary), but to really do the exercises in the spirit that the instructor intends, you should have someplace, like a sketchbook or a stack of cheap copy paper, where you feel comfortable making a mess of things. You don't have to show what you draw there to anyone else. Nevertheless, drawing there will help you grow and build skill. I hope this helps. I look forward to seeing what you make, if/when you feel comfortable posting your work.