Both sides of this "readability vs. performance" debate can be argued ad absurdum but that's not my intention. All I know is that I try to conserve resources no matter what level of the stack I'm working on and those generated snippets certainly don't!

Indeed, but they're not intended to. Nothing about Copilot's specs even claims it's generating optimally-performant code. And the Python example indicates why that may not even be a desirable output (most performant and most readable are orthogonal metrics).