I guess it's more about the actual source code. I'd expect that just hearing "how" something works can still allow you to do a "clean room" in a sense that most

I guess it's more about the actual source code. I'd expect that just hearing "how" something works can still allow you to do a "clean room" in a sense that most of the algorithms aren't secret and a lot of "how" is obvious to the experienced practitioners just from the description of the behavior.