I dunno, introductory level programming classes create an opportunity to observe anywhere from 5 to 200 people solving the same problem.
I've never taught a CS course, but back in my college days I helped a friend with his CS homework by taking advantage of weak file permissions to copy other people's homework. The shocking thing was that, looking at a small sample, most of the programs didn't work correctly. To complete the assignment our way, we had to fix bugs in programs that other people wrote, which is fantastic preparation for a professional programmer ;-)
But using introductory programming courses as an example of writing real-world code would be a huge mistake. Most of those assignments in my day were almost trivially easy for someone that actually understands the material (and almost impossible by those who don't). It would not be a fair assessment of software engineering productivity.
Worse, the homework assignments are generally completed outside of class under widely ranging conditions. (One student finds a quiet spot in a library, another is in a cramped dorm room with a roommate practicing trumpet, and another goes out and parties until dawn and tries to crank out a project three hours before it's due.)
In your attempt to weed out conflating variables, you introduce a similar variable... namely: all programmers working in the same conditions definitely reduces external stimuli which could impact performance, however it introduces a different variable in which the some (or many!) of the programmers are no longer working under their preferred conditions dropping their performance.
I've never taught a CS course, but back in my college days I helped a friend with his CS homework by taking advantage of weak file permissions to copy other people's homework. The shocking thing was that, looking at a small sample, most of the programs didn't work correctly. To complete the assignment our way, we had to fix bugs in programs that other people wrote, which is fantastic preparation for a professional programmer ;-)