If I remember correctly, HS5 hypothesized that the R-Hop does well because it aligns or encourages the alignment of the geometric center with the actual rotational axis. He called it the "Wobble Hypothesis".
https://sites.google.com/site/hsarmo...effectiverange
He theorizes that R-Hop reduces excess up and down movement, allowing it to maximize forward distance.
Perhaps this is why similar hop-up systems seem to have flatter trajectory, because it is more "efficient" and you don't need to over-hop it to get the same range.