They said that the course takes place in the upper atmosphere of the planet, apparently in a planet with a relatively light atmosphere in general. All the ships have a TWR over 1, otherwise they wouldn't be able to land on planets anyway, so their maneuvering thrusters must be able to compensate for gravity.
But you're totally right, the EVA weightlessness is kinda bonkers though. Haha. It's really just a pretty piece of scenery though, let's not get too engrossed in physics details. =P
In other news, I've been practicing flying and my best racing time in my 350r is 1:42 on Vanderwal now. Not bad, but still not super fast. World record is 1:02.17. It's still really hard and the IFCS seems totally out of whack and it tends to oscillate the craft, but at least I'm having some fun!