You’re talking about code that’s been reduced from 10 lines to like a one-liner; whether it becomes more understandable or not (and whether to keep it as such)

You’re talking about code that’s been reduced from 10 lines to like a one-liner; whether it becomes more understandable or not (and whether to keep it as such) is a matter of taste. But not copying and pasting code by merging common logic is a matter of reducing the number of times you can fuck up, and reducing the number of “accidentally/unnecessarily special-cased” scenarios. You’re trying to reduce the amount of information needed to understand the codebase. The former is preserving the information, it’s just writing it more densely.