Good question, but isn't it said that e.g. for bobsledders weight is important, or is this just because more weight will put more pressure on the ice and with this melting is better?
There's more factors involved than just the weight, the rolling resistance of the tyres and the axle friction would also be a source of potential bias.
I notice they re-used an old special for the bigger cart, with new printing, but kept the same number ( 2 ). Isn't that slightly stupid?
The current green easter egg (I got one in Normandy) boy with cart makes a third possible racer. Now I have two carts I'm very tempted to go and get one of these sets. I'd like to see a girl racer as a nod towards equal opportunity.