I'm all for reducing DSP use and having S1 be as efficient as possible in using resources, but care needs to be taken with comparing the behavior of AAX plugins to VST and VST3 plugins. I wouldn't be surprised if there aren't some optimizations that Presonus could do for VST3 plugins, but the fact of the matter is that the vast majority of CPU use by plugins is a result of the plugin software sending instructions to the DSP/CPU.
From what I've observed Studio One's Performance Monitor is not measuring real CPU utilization (at least on Windows 10) or disc I/O for that matter. I assume that it is some measure of how much of the DAW's DSP has been consumed.
When you load certain plugins (I'm looking at you Waves Abbey Road reverbs) they consume a bunch of S1 "CPU" just idling. As an iZotope user, I know for a fact that S1 "CPU" use dropped significantly when the latest versions of Neutron & Ozone were released.
I'm all for Presonus implementing as much of the VST3 protocol as they can - just as long as it doesn't break anything - and we should continue to demand that they do so. That said, just keep in mind that AVID uses a proprietary protocol for their plugins, AAX, and can enforce how it works, while Presonus has to support VST and VST3 protocols that they don't control.