I read about Landauer's principle and was wondering about the implications from it's original derivation. Landauer derived his principle straight foward from the second law, but I see people favoring derivations by Shizume or Piechocinska, who derive it without direct reference to the second law from the microscopic set-up.
I wonder why their derivation holds stronger than the one derived directly from the second law. Is it just circular reasoning to use the second law, which is subject of discussion, to prove the principle or may there be an even more subtle reason?