Jorge,
   Yes opening the anterior hip can help with butt wink.  You can determine if butt wink is a mobility issue or stability issue by kneeling on all fours on the floor.  Make your knees as wide as you normally squat and rock back until your butt sits on your heels.  Either film this or have someone with a good eye watch your hips.  Start by doing it with no ab bracing at all.  You should see your hips butt wink.  Next, brace like you would with a squat and go again. IF your hips stay solid with bracing it is not a mobility issue.  IF they still wink, you are most likely looking at mobility.  You can also play with this to see what your ideal squat width is.  This is a Dr Stuart McGill strategy (I think. He uses it to determine stance width).  I’m not sure if you can find a video of this online.

   Hope this helps.