I still don't see where flying inverted at speed is going to help a beginner when he can just get someone else to fly for him

This is based on Bonneville Salt Flats and FAI (real plane) speed records.  A two-way average.  A little bit more challenging than just one-way level flight. 
But still somewhat less challenging than the proto/carrier style of speed that demands a light model and non-sagging acceleration.
This is not exactly for "beginners", it's more for modelers who are not engine builders.
I don't think you can find anybody at The Brodak who can't fly both ways, and if there is he can find a pilot.

I agree with Skip if some one is going to enter Sportsman Speed they should be the pilot.   Learning to fly inverted is not that hard except in a balloon burst meets we had many years ago us experts had to attack the balloons inverted.   After about a dozen laps I was dizzy, go figure.  Had to go up right to get over the dizzies.   AMS pattern calls for 6 inverted laps and I have been flying at least a dozen laps or more inverted to get used to it.