" So it's still not really happy on the highway. "
I assume you got that from here? From a motojourno that is used to liter-plus sportbikes and porcine, ludicrously overpowered wallet-sapping adventure bikes? A competent 4 cylinder DOHC fuel-injected 100 BHP 600-class sportbike would need to be downshifted to do a quick pass unless you are already taching 9,000 RPM and just buzz it up to its 12,000 RPM redline for a brisk 1/4th mile.
" It will cruise at highway speeds without issue thanks to the new six-speed gearbox, but if you need to make a quick pass, a shift or two are usually in order to do it with authority. "
What does not really happy even mean? We are talking about the LC452, a modern 40 HP, 6-speed, near 400 pound bike that will run +95 easily. A 452cc short stroke one-lung motor is inherently busier than a larger displacement engine. It's not a problem to the machine RPM-wise, but you will be rowing the shifter more than on a Goldwing or "KTM 1290 (160 HP, 600 pounds wet)". The venerable KLR650 doesn't even make 40 HP but nobody is saying it's not highway worthy. Nobody spends great amounts of time above a wind-blasting 75 on the highway except teenagers and "sport riders", it's just too expensive contributing to the local constabulary. A larger displacement machine will obviously seem less "hurried" at 75 MPH, but that's a subjective feeling not a mechanical limitation. Smaller engines will be buzzier than larger ones. As long as they aren't putting your hands or butt to sleep via vibration it's all good. Personal preference isn't mechanical limitation.