Here it can be seen that the plates have a two pixel gap from the bottom, and a one pixel gap from the top. This seems inconsistent with vanilla minecraft item positioning. This could be fixed by moving the sprite of each plate one pixel down.

that's probably because the texture isn't an even number in height

No? The textures are 16x16.

I think they mean the drawn region.

But yeah, the plate textures are 13x13. Ender pearls are odd-numbered dimensions as well. Wontfix.