I think you are confused with what you are trying to say.
And I quote...
"But I agree, whatever they do with hip-swaying etc, bad posture is just bad."
A male cannot hold a woman's posture.
Even the most camp male as our bone structures are different.
THAT is what makes us look different when performing the same actions.
If you look at Leilana at the ball in the formal wear you can see her head is too small for her body because her body is mapped to a man's frame.
Just like the video above the women to try can compensate with the body frame difference their shoulders are pushed forwards to try make their frame look smaller.
Hence they walk funny and unnaturally lol.
Warrior women should have more "manly" movements (for those that want to call it that) but general women don't move like that especially in that medieval type setting as they are "Ladies" thus are supposed to move with "Grace." These things matter.
Having legs open when wearing trousers is not a problem and acting overly feminine with the "sexy walk" with strong hip swaying is not what I am talking about.
I am talking about the basic issue of the male and female's frame is different even if the same height which then effects movement differently but cannot be captured in animation if only a male model is used.
But yes all animation needs improving which was my first point lol. 
As far as I know, Leliana has the same body as almost every other human female, so if her head looks small, so must Cassandra's, Josephine's, Vivienne's, and the Inquisitor's. But they don't, so I'm thinking it's just a matter of perspective. Her outfit is not mapped over a man's frame, in fact it's the opposite: The clothing made for a male is mapped to a female frame, making it look a bit odd, as I talked about previously.
Only women in high positions (or trying to please the ones in high positions) are going to walk "gracefully" as Morrigan and Vivienne do. And even then, we only know this is important in Orlais. I honestly doubt it applies in Ferelden or Tevinter, so don't assume what the cultural standards of Thedas are. I would actually say Morrigan walking that way proves my point. She doesn't naturally walk that way; she was raised in the wilds! She learns to move that way, for a purpose. It's not natural. If there were options for animation style, and you wanted to move like that, say to RP a noble with a strict upbringing, that's cool, but it's still instilled, not inherent.
The only reason I mentioned posture was because that quote was originally posted in a thread relating to posture. Why can't a man have the same posture as a woman? Posture =/= body shape. If a man can slouch or sit up straight, so can a woman, etc. PhroXenGold, above, talked about crossover between how men and women move, and that applies to bone-structure as well. There is a lot of crossover between bone-structures in males and females and therefore even more crossover in movement.
I think what me and them are trying to say is that there is so much crossover, so little true and noticeable variation, that having one (good) set of animations for both genders would be ideal given that the thought of having a choice between 3 styles of animation is somewhat idealistic.