I wouldn't call that study publish worthy.
It certainly isn't statistically significant. 4,500 lines of C# code is nothing. I work with systems that have millions of lines of code. I've seen single class files that have thousands of lines of code (and vomited when I saw it). An important question here would be whether the volume of code in a system is a significant factor in the value of refactoring.
Based on their own statistics the refactoring was poorly done. Their result was more code, more complexity, and more coupling. Certainly not the work I would expect from an experienced software developer, but certainly something I would expect to see from undergraduate students who don't fully understand what they are doing.
I think the last sentence in the actual study sums it up pretty well - "Furthermore, it would be better that the same
experimental setup can be executed in industry environment with the industry experts and with
the industry level matured source code."