I somehow feel like this person is talking about large-scale comic projects, major industry artists, and so on. They have a tendency to draw "what sells". It does seem like most major characters in main-stream comics are overly sexy in some way. It seems to be a thing in comics. Over-sexualize the women. Even in a lot of indie titles if it's coming from artists who are big in the industry. There has been a lot of work in the opposite direction as well, but aside from Rat Queens, Paper Girls, Lumberjanes, etc. They still aren't quite as big.
Now, this isn't the only factor involved. I think there is a cultural understanding of what a comic character should be. Kind of like a template for what they look like. Want a manga female -- use a sexy mini-skirt, or some kind of strangely revealing costume. Need an every-day teenager -- use a betty-veronica style supermodel base.
There are probably other small factors. But, as comics were largely a male dominated industry, it's going to take some time to come away from that.