HRX217 full throttle

On my HRX217, I've noticed at the "Fast" throttle, it's not at full engine throttle. I can push the lever just a tab bit more and hold it there for full throttle and the engine revs up a tad bit more. But if I let go, it goes back to the original "max" engine rev.
Is this normal in these mowers?

HRX217 full throttle