It is my belief that at the more extreme differences of matchmaking, especially for players who know their opponent, the stats can get pretty off. I know that I am much more willing to experiment with weird facs against bad players, and that means that for higher differences you can get some weird stats.
That said, I don't actually know what difference in WHR really means. A 90-10% seems to extreme for me, I think 66-33% would be ideal (though we might not have enough data), at most perhaps 25-75.
As for what I think this means?
Cloaky is good as a generalist, but not amazing. It is exactly what everyone thinks it is.
Shield is probably too good, but is perhaps a bit map situational. It tends to have more of a skill curve than I would expect.
Rover is maybe fine.
Spider seems fine, but gets weaker and weaker as players grow more skilled. Its probably falling behind in the eco game when people are really trying.
Tank is probably a hair overtuned still, especially for weaker players.
Amph is situationally OP. Like everyone probably thought.
JJ is perhaps good for crushing people worse at the game than you, or getting surprise victories. Results seem to be unusually swingy, an cannot tell easily why, might just be a quirk of lower number statistics.
Hover is forgotten by many, just like I almost did. It is probably generally a bit weak, with situationaly good maps that experienced players can recognize and make the most of. Could probably stand to be a hair easier to use.