But the divergence is more often than not unintended and causes inconsistent/ unexpected behaviour when a change is made in one copy and not the other, which is why it ends up using up more time in the end.
And how is extracting a few lines of code into a function and calling that more complexity than having two identical copies of it?
When the divergence comes from subtle differences in requirements, then those subtle differences in requirements now need to baked into your single function (or, really, broken out from the function; but they have to be recognized as different to begin with). Now, the next time you need to address a new feature along one pathway, you must also be certain that you are not subtly breaking some completely unrelated feature requirement.
