It seems to entirely be about aesthetics. rather than any athletic or functional goal.
I agree. I think the idea of "ideal" physiques (eastern, western, and of course other parts of the world) is purely a matter of aesthetics. Iinm, however, a connection was claimed between the aesthetic preferences and the martial practices. Iow, that the reason for the different aesthetic was the desire for a particular physical shape that was conducive to doing the particular (Chinese) martial art. That connection is where there is a fundamental disagreement (that is illustrated by the photos you've posted).
The secondary argument --that has its own thread-- is that training and obtaining a particular physical form is actually unhealthy. That has some basis, if we consider over training. So, we can agree that some exercises may be unhealthy; but anything done excessively is fundamentally unhealthy in some way. Sitting is unhealthy.
However, where I do agree with the western v eastern cultural preference argument is that the body beautiful (body-builder) has been idolized in western art and culture in ways that it hasn't in the east. All societies idolized their warriors, who could come in all shapes and sizes. Ya got Samson, but then there's David and Joan of Arc. The west developed the cult of the athlete who was supposed to be god-like (an Adonis or Apollo). But, the physiques of athletes, as you point out, is determined by genetics, what and how they train, and nutrition. That's not counting the steroid driven bodies of body builders for the last 30 years.
"A man is rich when he has time and freewill. How he chooses to invest both will determine the return on his investment."