It puts the lie to the claim that the EU is to be a “club” of equals, just for one.
For another, there is the historicity of Germany and Russia collaborating, being in every case a precursor to a hot war.
Gazprom has always used its products as a political tool, whether it was raising prices or cutting off the supply. Bypassing them and going straight to Germany is the ultimate form of that, and the ultimate reversal of eight decades of hard-won peace.
There is such a thing as freedom of commerce. Anything to the contrary is speculation. In this situation Poland is clearly in the wrong, obstructing legit business.