Menu background texture cannot be animated

The bug

The menu background texture cannot be animated. This is in contrast to many other UI textures, which as of 23w31a can indeed be animated.

This happens regardless of whether the texture is added to the gui.png atlas.

How to reproduce

1. Download and apply the attached resource pack
2. Observe

Expected results

An animated nether portal menu background texture.

Actual results

This stretched mess.