When the elytra model and animations were made data driven, some of its visuals were changed. This caused a bunch of issues, which can be more easily observed in the gliding animation:

• When crouching, the wings clip through the player's body;
• When the wings are fully open, they're too far apart;
• When the wings are fully closed, they're too close together;
• When viewed from other angles, the wings can be seen attached to a weird spot.

The wings are also offset when swimming, which is an animation of its own even though it shouldn't be needed.

To fix this and match it to older versions and java edition, a change to the model is required as well as the animations. Instead of using animations to scale the wings, the cubes should be inflated within the model. Then the position and rotation can be tweaked in the animations. Check the corrected model and animations attached to this ticket.

If what's described is difficult to visualize, see the attached media.