Well the older fem figs were far less flexible at the hip and the knees were also lacking a good joint (not to mention the ankles). Heres my old breakdown-
https://www.mwctoys.com/REVIEW_101510b.htm
Then there was the improved aesthetic but horrible articulation on figures like the RE Sheva here
https://www.mwctoys.com/REVIEW_012910b.htm
Things have honestly improved a lot since the Sucker Punch girls came out.
There no doubt the old TTF bodies were bad in articulation....
However girls released since BW1 (and including BW were basically the new TTF body type). Most of the ankles are still the single ball joint (used since the old TTF) or the split-ball.
Some of the notable first in
new TTF development by HT.
1. First the new TTF body: IM2: BW
2. First to use split-ball ankles: RE5: Jill Battle suit
3. First to use stronger metal screw secured elbow and ankle joints: POTC4: Angelica
4. First to use a smaller body format (mostly just shorter lower legs): Babydoll
5. First to use double jointed elbows: BW 2
Future:
Probably first to use seemless elbow and ankles: RE4: Ada Wong
Every torso and lower torso have variants with every release, so that's many firsts on those 2 aspects, internal skeleton varies very little, I suppose... except neck posts have variable length as well.