Not sure if this is intentional, but it feels more likely as bug for me. I was recording a video and went in spectator mode underground in hope to look for an amethyst geode for my video. Well, I couldn't even see the shape remotely, nor the texture, but I came across what looked like a blob of blocks, seemingly strangely lit. Turns out that were backfaces of blocks that made a cave, and the lighting was caused by lava. One "block" also seemed to have multiple textures, like it was made of multiple materials. That were multiple blocks that shaped a corner. There are is z-fighting in models that are composed of double-sided texture where the model has two faces facing the oposite directions (like flower or grass textures and similar).