Simpler textures with few colors and pixels look buggy in the in-game inventory

When you look at the screenshot without a texture, everything looks consistent (just in general, keep reading), however other textures with blocks with a few pixels or colors, look strange in the in-game background, on any GUI interface.  

I also noticed that it doesn't just happen with textures, since in Minecraft vanilla itself when you look at the snow, similar stripes appear.

What I expected to happen was...:
It should be a uniform black background, with no opacity.

What actually happened was...:
Ugly lines and smudges, which are very annoying.

Steps to Reproduce:
1. Go to a flat area full of blocks with few pixels or, more importantly, few colors.

2. Open your inventory.

 

Observation: "Texture night" with nothing open, is to show the difference when you open it, a comparison.