Of course it's been known for a long time that copper is a better conductor than aluminium. What's new is improvements in copper die casting, which makes motors with copper rotors easier and cheaper to make.
https://www.machinedesign.com/news/article/21829687/industry-could-take-a-shine-to-copperrotor-motors
Yes, that was my point. If it would be cheaper to make, they would've switched to it, so something tells me that it is not cheaper. We are talking about companies that try to shave pennies off the BOM cost of ECUs.
Copper is getting stupidly expensive in general, and machining it is harder.
The other issue is the typical upfront cost of things. If switching to copper would add 500 EUR to the sales price of a car, and it would add 3% range improvement, who would buy that? That 500 EUR is very visible, while that 3% would be a range of 360Km instead of 350Km.
If people would think about long term running cost of cars, most people would drive a hybrid.