all of the above are the exact same block lab blocks from chisel dyed with ink!!

as you can see in 2 directions its solid black the other 2 are correctly broken up!

Black dye can make them appear very dark, even completely black. If a block texture is dark enough this will happen, especially on the x (or z, can't remember) axis as it applies 0.6F lightness in addition to dye darkening.