Thanks for the response on the motorcycle categories, Chad. Your explanation makes sense to me but motorcycles have been allowed in 590-592 for a few years now. The winner in 592 in 2021 was a bike, one finished second in 2019, another bike finished third in 2018, and a number of others were entered in these categories over the years but didn't place.
The rules read as you've explained them, but they don't appear to applied that way in practice.