Code that is purely utilitarian (see “useful articles doctrine”) isn’t a work of human expression that is copyrightable.
That's not really a factor in determining what's eligible for copyright protection.
I don’t copy/paste code from SO but there is sometimes inevitable duplication because sometimes there is only one right way to do something! Copyright can stray into the case of the ridiculous pretty quickly.
Is an interface declaration inherently different from, say, a merge sort implementation? It’s all code. But they also serve very different purposes. I do not think prior to Google v Oracle there was much case law to distinguish between different types of code, but in the industry we recognize all kinds of nuance.
I always thought that code snippets that small are not considered by the Courts to be eligible for 'copyright protection'.
https://twitter.com/DocSparse/status/1581461734665367554/pho...
Adding to that: How many people here actually abide by the StackOverflow contribution license of CC-BY-SA when copying and pasting code from there? ;)