It could be an easy way to create overlays for blocks. Of course it would not work for every blocks but it could reduce the amount of texture a bunch for some blocks.
It would require to get rotated textures for overlays but by doing so, it could be possible to use significantly less textures. I'm guessing it is possible to use only part of a texture for doing this.

Using only 3 textures, you could have
One texture for block that are surrounded
One texture for x and y overlays. It would make it more useful for texture like planks logs
One texture that would be both corners.

Here is a little template I made as an example

I don't know how efficient this could be but I'll let you be the judge.