Yes, that is correct. It’s a gradual electrical degradation if you will, vs complex combustion and mechanical limits. With electric you can somewhat trade voltage for current to keep from hitting a sudden cliff as Greg said.
The big implication is that an electric motor has a huge advantage with the total area under the curve since a combustion engine needs to spin at some minimum speed before it makes any reasonable amount of power. The electric motor doesn’t need to use those clutches or transmissions to match engine speeds to ground speed to get you moving or out of a curve, since it has torque for that in spades. However it does fall down eventually at high RPMs as shown. When very high speeds are required, a 2-speed transmission can be used to make up for this (e.g. Porsche Taycan), or you can use multi-rotor motors that has part for slower speeds, and part for higher speed. I don’t see this as an issue with use on a sprint kart. In my case I will need to run a 1:2 gear ratio, to slow down the output.