I doubt you could put Dougie Lampkin on a Super Bike and expect him to win the IoM TT, or for that matter put John McGuiness on a Trials Bike and expect him to be class topping at a 6-Days trial either.
I'm not sure what your point is. I'm not talking about different cycling disciplines, just like your example, an XC rider is never going to win a DH race and a DH rider is never going to win an XC race. But we're talking an XC race and an e-XC race. If all the XC riders did a race on acoustic bikes, then did the same on e-bikes, I can't see there being much difference in the result.
Dunno why you were talking about motorcycles anyway, this is about e-assisted racing. Which to me seems pointless. A bit like say, e-assisted weightlifing or e-assisted marathon running....
It was a comparable example of different disciplines in outwardly the same sport that came to mind, also includes motor assisted movement...
e-XC and XC are different disciplines, they don't race against each other.
Manipulating the motor assistance and handling the increased weight is part of e-MTB racing that isn't part of normal-MTB racing.
The motor assistance also makes fatter tyres more suitable for XC, where you may have gone for a 2.4 instead of a 2,2 for a technical track, you might be looking at being able to use 3" tyres which further helps on roots and rocks as does the extra speed, this may mean that a rider who is better on less technical tracks does better over technical features than they normally would.
It would be interesting to see current XC racers do one race normally then another race on the same track with e-XC bikes.