Yes. Gilding is a luxury finish that applies a colored/metallic film to the edge of the pages. Since the cutting of the block is a mechanical process on high-thickness paper, natural micro-textures may arise on the side surface.
The Visual Effect: When applying the foil (which is shiny and reflective) over these edges, any small mark or streak resulting from the cut tends to become more evident due to light reflection. For this reason, these slight marks are not considered manufacturing defects, but rather an intrinsic characteristic of this type of manual finish.