So because he doesnt do it with every character it doesnt matter? He's a professional, and he takes liberities where he can. He realizes what his target audience likes, and in Japan, it isnt huge boobs right now. He designed Aerith too, didnt he? Her breasts were normal size.

He probably refrains from doing so anymore because people cant focus on anything else. "omg boobz she's a hoe" and so on.