Malgus, another possibility for the sheetrock is just aesthetics. The back half of my house was a kit and so all of the wood is finished very nicely. That’s pretty much the story with all modern log homes. The front half is what some log restoration folks called a real log home. I had hired them to do some work for me when we bought the place. Apparently the logs came from the property and the house was built log by log without factory finishing, only what they did themselves on site. I suspect the interior was very rough looking pre-sheetrock and either the original owner or a subsequent owner covered it over with sheetrock. Even then, having two layers would still be a mystery though.