There are a lot of pretty complex prompts, where if you asked a group of reasonably skilled programmers to implement, they'd produce code that was "reformatted and changed variable names" but otherwise identical. Many of us learned from the same foundational materials, and there are only a handful of non-pathological ways to implement a linked list of integers, for example.
With code it may be more obvious, in that you can't as easily obfuscate things with synonyms and sentence structure changes. Even with prose, there is going to be a tendency to use "conventional" language choices, driving you back towards a familiar-looking mean.