Kotaku makes it sound like the devs are saying female characters are just somehow more complex technically than male characters, and they literally didn't have the technology before to create them.
What they're really saying is that it would be twice as much work with two different modeling and movement algorithms running instead of a single, streamlined approach. It's not impossible, but considering the amount of work developers already have to do and the graphics the games are running, it was left out in favor of a smoother, finer experience.
What you noted about creating an engine to support custom characters means that those developers took the time to go back, refactor existing code and optimize around different multiple different models running simultaneously while keeping a smooth experience.
What you noted about creating an engine to support custom characters means that those developers took the time to go back, refactor existing code and optimize around different multiple different models running simultaneously while keeping a smooth experience.