These are just natural variations in the wood.
Essentially they are marks from imperfections that have almost been shaped/sanded out during the making process.
they may or may not have a firmer feel, they might actually make the bat perform better.
until you have tapped a ball on it, hit it with a mallet, knocked it in, and played with it a few times, its impossible to tell whether you will get on with it or not.
It is however, very rare nowadays to find a total plank.
Pressing this again will only exacerbate any existing firmness that might be present from hard bars, its not something I would recommend at all.