>>1512320this is unfortunately the truth. well, the part about breasts limiting movement--the second part is a lie.
most these videos are, for the most part, very easy to make. load a model, motion, stage, apply shaders, and you are done. fixing arms clipping through breasts is not something most of these people want to do as it takes time and skill.
without soft body physics MMD will not have better than second rate breast physics. breasts squishing against an arm is almost out of the question, so defending against clipping with physics does not look good and you must edit the motion itself.