The main principles had been (a) cheap materials and (b) easy to construct. However, what most people are referencing as “Khruschevka” are actually the houses built during Brezhnev years. The first Khruschevkas (I lived in one for few decades) had been built from the relatively small and rather thick (important during both winter and summer) concrete blocks while those of Brezhnev period had been made out of the bigger and thin concrete panels (window being a part of a prefabricated panel). They were easier to construct and probably cheaper but termoisolation was much inferior and, IIRC, the cellings were lower. Cracks of the panels were known problems for some of the models.
I didn't know about the change to the wall thickness. Very interesting. And I am totally unsurprised that they cut back...
fasquardon