That reasoning is weird to me. I could live with "there is no impact for users on this" but if it has impact for users (there of course is a difference between

That reasoning is weird to me. I could live with "there is no impact for users on this" but if it has impact for users (there of course is a difference between developing a library where a lot of things have impact from a GUI application where most things are invisible to the user) it should be documented, even if documentation takes three times the time. Good documentation is part of a quality product.