When I was in college I was attending a course teaching to build C++ project, the professor checks plagiarism by checking the creation date of source code files, since the project was built step by step with new files being added progressively.
I was being perfectionism about my code and did a lot of refactoring before submitting the project, and got a very low score because the professor saw the dates of my files were new and all the same and thought I copied my homework from someone else. While the ones who actually did plagiarize the homework got high scores, because they copied other students' source code lesson by lesson.
My professor obviously did not even read the source code of our homework, otherwise he would easily know who was writing original code and who was just copying.