I'd fully expect it to copy code and change variable names in a lot of cases--if it wants to achieve the goal of filling in boilerplate, how could it do anything else? That's pretty much the definition of boilerplate: it's largely the same every time you write it.

What's less clear to me is that Copilot regularly does that sort of thing with code distinctive enough that it could reasonably be said to constitute copyright infringement. If somebody's actually shown that it does, I'd love to see that analysis.