To illustrate, google translate got suddenly better some time ago when it searched literary texts for phrase matches and then cross-referenced known translations to give you a translation.
Copilot is perhaps doing something similar (somewhat as an analogy) copilot could maybe be finding exactly one sample that it suggests, in which case there could be attribution.
It is unlikely to offer any solution without a consensus. To further the example, how can you be confident in that translation? What if there is not just one literary match, but many thousand and 99.9% agree.
Without that high match percentage, it would be difficult to know if the result is a accurate, or with a small set of disagreeing matches, again it would. E hard to give an accurate answer. I don't know for sure, though seemingly copilot would have some threshold of agreement across multiple matches before it suggests a solution
It's like saying, I know 'polo' comes after Marco not only because I was at your pool party where we all signed NDAs, but also because I've been to dozens of other pool parties. How do I know where to attribute this knowledge? In part that knowledge is due to the prevalence of examples and not just any single example.