Average or peak?

Making something that performs well at freeway speeds, yet also is efficient when manuvering round a parking lot is hard.

Most companies just hope you don't care about only getting 5% efficiency round the parking lot, because that isn't a large fraction of your energy budget, even when it's so inefficient.

Airflow losses in big AC generators are solved by having the whole motor sealed in helium. The helium gas is used as a coolant too.

It would be hard to design such a system with a big enough supply of gas to survive leakage for the whole life of the motor though.

The early Model S motors had problems like that. They got a lot better over the years. The Model 3's is great, and the Model S/X front motors are now the same as the Model 3's, while the rear motors are something else that's still a lot better.