I think there's a large difference between copy-paste and what you're describing (which I'll dub 'manual transcription'). I have no formal training in learning or cognition, but I do have quite a bit of personal, anecdotal evidence to suggest that manual transcription is far more useful, from a pedagogical standpoint, than straight copy-paste.
Rather than take a boring example from my programming career I'd rather draw from my brief mathematical studies in college. In undergrad I was taking a course on Real Analysis. The course redefined, much more rigorously, certain concepts that I had understood at a much higher level--think the limit, derivatives and the Riemann Integral. Suffice it to say that these new concepts challenged my understanding of introductory Calculus, and when I was tasked with writing proofs based on the underlying concepts (e.g. neighborhoods), I struggled.
In what can only be described as frustration I decided I was going to start copying the proofs over and over. I repeatedly transcribed half a doze proofs for a few days straight (I did each one a few times each night). A strange thing happened. I began to understand the proofs. By that I mean I started to understand the intuition required to make the transition between each step of the proofs. At that point I found the material much more accessible. Reading the book was easier, the lectures made more sense, I could do homework, and consequently I could complete the exams.
I like this example because there is no copy-paste alternative. I had to engage with the material, but I chose to engage at a very mechanical level. Still, there was something about the process of reading and writing that aided in understanding the material.
I don't believe you can get that with copy-paste unless you find some other way to engage with the code.