I’m pretty sure the modern hourglass and inverted triangle art references look identical due to aesthetic homogenization triggered by Japan’s 1937 invasion of China and the fall of Nanking. This conflict dismantled traditional Asian art institutions. Post-war, rebuilt media industries adopted Western commercial ideals. Today, reference artists apply identical stylized curves (cinched waists and padded hips) to both figures, flattening the inverted triangle into the hourglass template.

But I could be completely wrong, I dunno