Sure, the posted speeds would be lower if the rules forced straight and level entry from XX distance etc. But they don't, they allow diving entry before the timing course, and I don't think anyone disagrees that gravity sure helps the numbers. If a set of rules for straight line RC speed existed that were common to AMA and MAAC, we could have our own events if there were more than three people interested. I bet a few would belly up to the bar. Right now F3 speed seems to be the only game in town. And gravity or no, they break a fair bit of hardware achieving these results so it isn't a cake walk. But I agree it doesn't represent straight and level flight potential.
The MB40 powered models are impressive.. whether pylon models flying straight line or the dedicated speeders. What a potent power package.