I had something similar but convinced the other person the rest of the work can be done later. Then the person went ahead and did it despite the other instances having no use/value. Go figure. I guess having consistency has some value to argue the other side. I tend to be extremely flexible in terms of allowing different ways of doing things but some seem to confuse form with function insisting on some "perfection" in the details. I think this is partly why we get these very mixed reactions to AI where LLMs aren't quite "right" (despite often producing code that functions as well as human written code).

Consistency reduces the mental cost of acquiring and maintaining an understanding of a system. In a real sense, moving from one approach to two different approaches, even if one of them is slightly better than the original one, can be a downgrade.

Like many other things it's a judgement call. The break down occurs when people replace judgement with rules or "religion". This tends to happen when they don't have the experience of seeing the long term impact of decisions in various contexts.

In a way, simplifying the judgement call to the black-and-white approach “either you change all instances or none” without considering nuance is also a way of managing the mental overhead. Making a simple call lets you spend all your nuance energy in areas where it might matter more.

I agree that it’s also a way of accumulating technical debt, it’s all a bit of a tradeoff.