If you cant visualize them "understanding how to draw figures" is called making stick people. Knowing that people have libs and joints doesn't go very far.

This is blatant misinformation. Inability to visualize does not mean inability to understand geometry. A huge amount of figure drawing is just understanding the geometric relations between different parts, or at least using geometry to draw the scaffolding for making a coherent anatomy. Being able to visualize things does not at all correspond to putting it on a page, as literally anyone who can visualize things will readily tell you.

Which is thicker, a torso or an arm? Which is longer? When you stand straight, are your hamstrings and quadriceps oriented on the left and right of your legs, or the back and front? Is you calf thicker at the top or bottom? If you put your palms down on the ground in front of you, do your thumbs point towards or away from each other? In degrees, about how far can you turn your head?

Someone who can visualize but has not internalized the answers to these questions already would need to look at themselves, maybe even try out the pose, to answer (and look up the muscle groups). That's just the same as you, and once they have the answer, it is still just words, something that you can contain in your head just as clearly as them. They can use those words to produce images in their heads when they want to, but that circles around to sketching. If you know the answer to questions like this -- and internalizing those answers, those mere "words," is a significant element of study for beginning art students -- you can draw figures that are significantly more accurate than stick figures. It'll look like garbage at first -- in part because you won't know which questions to ask -- but that's what it means to be a beginner in any field, drawing included.

"just sketching things out " doesn't work when you don't have muscle memory in your hands. Dysgraphia means that every finger movement must be coordinated from scratch. I literally cannot write my name the same way twice if I have 50 tries.

The sketch I mentioned is a reference sketch so you have an image in front of you that conveys the spatial relationships (i.e. the composition) you are going for. It's not a matter of making an identical drawing twice, because if all you wanted to draw was something identical to the sketch, you could just use the sketch.

There is certainly the matter of certain elements of technique being much harder with that condition, but it really has no bearing on the validity of sketching unless you are in desperate need to make the finished product as quickly as possible (because it does make everything slower, certainly). Even then, you should probably still sketch because you won't get to the end faster by fucking it up.

I'm sure you would tell me that your handwriting is terrible and irregular and I'm genuinely sorry you need to deal with that, but it's not just as bad as when you were six years old, right? And why is that when you lack muscle memory? I'm sure you can tell me quite a lot, but I am confident in saying that a major factor must have been getting a better understanding of the characters you are trying to write and what it is like to write them. There are things automatic fine motor skills would elide that the typical person relies on and you can't, but there is still surely a great deal you have learned (and a great deal you hypothetically could still learn) to improve your handwriting, even if it would remain irregular and you would write more slowly and with greater strain and so on.