Here's my take after riding with one.
You are correct. But, when you already have to much pwr down low. Right now I would have to say the banshee flywheel is overweighted for most riding. When the banshee comes on sooner it's less likely to break traction because the pwr hit isn't as hard. With the heavy flywheel it takes to long to spin up. Then when it does it's nuts. With a lighter flywheel the pwr comes on now and is more controllable to the rider.
We said the same thing... it just effects the banshee differently than the example for traction you provided. I know it doesn't sound right, but on the banshee it works. On a trials bike... heavy brass is the way to go.
The banshee fires twice in one revolution. The crank isn't different but the pwr delivery sure is. The weight of the flywheel becomes useless sooner on a banshee (opening a new can of worms).
A great thing about the lightened flywheel in the woods is the pwr is right now and doesn't show up so unexpectedly. Not have to hammer on the gas waiting for it to go as the four strokes roll past you. You can run into the corners faster and brake later. A lot of races are won by the person who brakes the best
*** NOTE ***
The only think negative about the lightened flywheel can be drag racing in sand at take off for a rider over 200 to 210 lbs. When you drop the clutch that weight can help get you out of the hole. After the wheels are spinning and the quads rolling.. the lighter wheel can benefit during shifting because it spins up faster... again, it's give and take.