Theu have an IMU, what they don't generally have is the various aspects of touch.

Yeah but imagine yourself lying on the floor with your vision being your only sense, plus an info floating in your mind: „fyi, you are no longer upright“.

That’s all, you feel nothing else. Now your job is to move all parts of your body in just the right way.

It is also things like "I can feel that my left knee is bearing a little too much weight, I should shift weight to my right hand and use that to push myself up" - things that come automatically to animals after learning the hard way in infancy (some of it is innate; baby animals are clumsy, but usually more mobile than human infants). Regardless of learned-vs-instinct, these abilities rely on sophisticated "sensors" and cognition. I suspect engineering the sensors is actually a bit harder, but I'm also not optimistic about a deep learning approach to the cognition.

A significant underappreciated advantage of animals over AI: lifeforms can "learn the hard way" more easily than 2020s robots because of cheap self-repair. AI labs are reluctant to damage their robots, but an essential part of humans learning to move safely is severely bonking your head and reckoning with the consequences - "hey, dummy, why did you trip and fall and bonk your head? Because you were running like an idiot."

I am learning the hard way to this day :) I have been practicing with work knives. A few months ago I got stupid and impatient, and sliced my thumb nastily. If I didn't block the cut with my thumbnail (still ruined) I might have chopped bone. It is hard to say precisely what I learned from this experience - "don't be stupid and impatient" is facile - but I know I learned a lot. I am actually optimistic about targeted surgical robotics. But for a general-use humanoid robot, I would not want to give it a knife if it's not capable of feeling pain. I never use big knives anywhere near my cats because I understand intuitively that they are nimble and unpredictable and easily stabbed by knives. I didn't need to be trained on this. A robot kind of does. Yikes.