Baumschlager said himself they tested with Aigner back to back driving R5 and electric on same stage and electric was 1s/km slower.

One simple way would simply be to turn on more power (that the car is easily capable off), say 50?hp more?
On the other hand the Rally2 is "top spec" developed over many years, the electric car is still a "semi-works" prototype. So maybe they can make it faster by other improvements.

Also the electric car afaik still uses same basic Fabia shell/chassis. Guess it could be more optimized if build from ground up.