Well, depends on what the line is, right? Like, you'd have a hard time copyrighting

int i = 0;

because millions of people write that line of code.

But if it's something unique and, say, identifiably Microsoft's code, then yes, you probably would not have legal grounds to stand on.

In the context of the OP, of course, if you're using an LLM just to write int i = 0; then you might be stupid. But possibly if you're using LLMs to do tedious tasks like writing unit tests then you might be able to argue that they're generic enough to not infringe copyright even if the legal situation is resolved in favour of LLM output belonging to the IP holders of the training data. It's just a legal grey area, which is presumably why so many projects are concerned about merging LLM output.