Because of the way textures are rendered in Minecraft (and literally every program in existence), images of the same resolution as their defaults that use less color variants won't be any less intensive. The only thing that would affect performance when it comes to non-bump mapped textures would be resolution and even then, as long as you have enough RAM to load said textures, you won't see a frame rate difference anywhere outside of 0-7 FPS depending on the RAM's speed on any 64-bit computer in the last 12 years. If your computer is more than 12 years old and has gone unmodified it won't be able to run this game in the first place.

Chunk loading is completely unrelated to texture size or complexity.

This texture pack sin't 8x8, it's 16x16.

Aside from the purpose the pack was created, it still looks disgusting and even if it could produce higher frame rates, it wouldn't be worth it to play with.

There are so many other packs like this. It's basically a bucket fill pack. Low end pc's will barely have a difference from this pack anyways. It's not really the textures that lag them it's the fact that they have to render layers and layers and some computers/laptops can't handle that.