That's not roleplaying, that's the basics of how you handle stuff like this. For lower-division level technical assignments, there's only so much free expression to extract signal from with regards to copying per assignment. Any individual assignment could likely be appealed as coincidence. If the same students turn in 2 more assignments that are suspiciously similar to the same other students, then you can have a pretty iron-clad argument for cheating.
Students cheating at lower-division university level courses is almost entirely a symptom of the students being poorly suited for the course material. Students who are interested and capable, but overwhelmed with the amount of work tend to just turn in incomplete assignments, or not turn in work at all. Encouraging the cheaters to drop while they can still get "dropped" rather than an "incomplete" or "F" is in everyone's best interest, as it provides an opportunity to consider a pivot to something that interests them more.
IMO, the overreaction by the professor was seeking further penalty for students who already dropped the course, or who would do so when confronted with their misbehavior. A student who cheats in CS is not necessarily a student who will cheat at chemistry, or business, or journalism. If they've already dropped out of CS, there's little benefit to be gained by pursuing the matter further.