I hate when game companies do this, hiding critical information from us like that as a ploy to sell strategy guides. (Which doesn't even work because GameFAQs exists nowadays.) Actually, I jest a little, I'm aware displaying 12 stats instead of 5 would make for enormous clutter while hardly accomplishing much.
Anyway, on to the subject at hand. A few sample pages of the Japanese strategy guide have appeared, and they gave us valuable information. Stability and drift are no longer around compared to MK7 (presumably being absorbed into traction and handling), making room for anti-gravity speed and anti-gravity handling. So if anyone was wondering what the point of anti-gravity was other than cosmetics (aside from the speed-boost-on-contact nonsense), boom, here you go. Of course, water and air speed/handling make a return as well.
There are a few things worth noting, though. In Mario Kart 7, everyone had the same water speed, and lightweights were faster in the air. That is no longer the case: as far as characters go, they have the same speed everywhere, with the difference entirely defined by the vehicle. What this means is that heavyweights are now faster everywhere. Yes, even in the air. Yeah, I know, that makes no sense. Welcome to the era of everyone playing Wario/Bowser/Morton, everyone. Same applies to handling: in MK7 all the characters' land handling was better than their air handling, which in turn was better than sea handling. Now each character has the same handling stat everywhere, and again, the difference is solely defined by the vehicle.
As an added bonus, it seems that the characters in each weight class, as well as sets of vehicles and parts with identical visible stats, also have identical invisible stats. So, for example, the Circuit Special wouldn't be superior to the Sports Coupe because it has better anti-gravity speed, which is what many people feared when hidden stats were first confirmed to appear.