You are working quite meticulously along a detailed morphology of primitive building blocks of the body - which is fantastique, as it builds intuitive understanding of how the body functions in space.
Now in your self-critique you mention, that you feel like you almost plateau-ed or are even regressing, especially in your 2 minute works. You also mention feeling stiff and awkward.
Now, in a way both can be true at the same time. Being very focused on precise measurement and 3-D forms allowed you quick progression in the past, that is now slowing down in visual progress, as you are pushing limits. But off course, that same focus also shows in the results. They don't look playful, excessive, flamboyant, expressive, because that isn't part of your specific project right now.
Your results do look impressive to those, that are on a similar path, and can savour the effort and discipline, that went into them, but that is a rather narrow audience. On your overall art journey, you have to remember, that those designs are mere etudes. You don't focus on combining exact measurement and pose, so you can put a frame around it, but so, that it becomes natural to your craft and you don't have to focus so much on that in later works, and still reproduce it.
To overcome the feeling of plateau-ing and stiffness, the best advise could be to relinquish focus for a bit, and draw something else, where precision and morphology aren't in the foreground, so you can get an impression how much your skills already improved, when you don't stress about them.
If you want to keep up with daily practice, you could just switch focus for a while. Just some suggestions: line economy, line quality, shadow forms, shape design, value separation, drawing poses from imagination or manipulating poses, that are drawn from observation, drawing from memory, attempting to impress a small child with your drawing, drawing the same thing in 10 different ways, ... these all would be alternative areas to focus on. They wouldn't advance your current focus much, but would add a reprieve, something else to do, to not get stuck in a rut, and meanwhile widen your artistic toolset.