Semitransparent pixels don't interpolate properly on animated textures where interpolate is set to true

To Reproduce:

1. Create a resource pack and include an animated texture where sequential frames are identical except for a different opacity.

2. Set “interpolate” to true in the animated texture’s mcmeta file.

3. Observe the texture not interpolating

Expected Result:

The alpha value is interpolated in the same way the RGB values are, resulting in a smooth transition from one opacity to another.

Actual Result:

The animated texture behaves as though interpolate is not set to true, where each frame is discrete.