That's experience speaking right there.

When I drew the strip I intended to pixelate the girls' lady bits once it was colored, but then I figured the scene worked better with big black censor bars.  Rule of thumb: If you want to highlight that characters are nude, if you want to draw attention to that fact – censor them. The more obvious the censorship is, the better.

Speaking of which, the figure in the middle is up for interpretation.

Fenix no. 6, 2005