Yes, it is perfectly normal and expected for this to happen.
Since birch and pine are 100% natural and organic materials, they have intrinsic and unrepeatable characteristics, such as the arrangement of the grain, the knots, and the base tone of the wood itself. As no two pieces of wood are exactly alike, the way the material reacts to and absorbs the coloring process also varies. More porous areas tend to absorb more pigment, while denser areas absorb less. This results in slight tonal variations, even when the same catalog color is applied.
These natural characteristics are not considered production defects, but rather proof of the material's authenticity and nobility. It is precisely these asymmetries and textures that ensure every album or packaging produced by DreambooksPro is a truly exclusive and unique piece.