Interesting information! Did you check the link to the article? Perhaps higher speeds on SF12 are handled ok if you always have a few gateways perpendicular to your line of travel (mitigating the doppler effect).
But nice to hear anyway. I can however note that if I drive from home (where the gw is placed on my roof) and off a few km I get very few sends going through. But if I stop the car and sit for a few minutes, in any particular spot it seems, I get a frame through.
Note that this is our private network with just a single gateway.