You'd think that, but it is literally impossible for it to be so.
The population of Western Poland, Pomerania and Silesia (The former Prussian/German regions) were settled by Poles expelled from the Kresy region (modern Ukraine/Belarus/Lithuania) after WWII. This means that Poles today living in Western regions inherited the same political/social/whatever legacy as Poles in Mazovia, Lodz, Lublin.
I really have no idea why these election results are so consistent.