No, that's not at all what they did. There was no proper scaling done at all. That's precisely what I'm talking about. If the model was actually scaled, and not simply a screenshot enlarged and eyeballed, that would show exactly what the problem would be. As for the hit box, yes, it is a standard size for all models... but scaling up the Au Ra female to the same height as the male would put it's parameters outside the hit box. The fact you can't understand the first two points means you definitely wouldn't understand a technical explanation with jargon.
Not having male miqote or female Roes was not a design choice, that was a simply a choice, or more specifically a content choice. Once they decided to add those two genders, then they made design choices about them (though to be fair, the female Roe's design was already decided with Merylweb) about how they looked.It was a design choice to not have girl Roegadyn or male Miqo'te, and we've got those in the game now, not like this would be the first time devs have gone back on "design choices".
When they decided to include the Au Ra (a content decision) they made a choice about how they would look (a design choice). And that choice was that females would be much shorter and more petite than males. If they had wanted the females to be able to be as tall as the men, they would have designed it that way. But they didn't.