I can see why you intuitively think that's the case, but is it really?

I don't understand how you imagine you can "isolate code" while making it less DRY. If I need to do certain functionality from some function, I need either to call other function to do it (if you already have a function that can do it) or copy that functionality into the function itself. The first approach is DRY, the second isn't. But I don't think second approach is a good idea, like, at all. So if I assume you don't mean that, what do you mean?

I can understand you can make code easier to test if you make it less DRY. Let's put that aside, because it's not really a big deal in this discussion. But the other three - I would love to see some specific example where making code less DRY will increase ease to understand it, and also possibly replace it and re-use it (provided we don't care about elegance of the result, since it would be taken care of by subsequent refactoring, as I already explained, so we can for instance copy-paste the existing code for the purpose of change).