As for the no harm/no foul stakeholder thing of classing the 28mph bikes off paths- you might see it differently if you owned a 28 before laws or were a dealer sitting on a bunch of 28's after law was put n place.I ride a regular bike and my wife rides a PAS Haibike. I really like ebikes and will buy one for myself at some point. I do think that, in general, people that go from riding a regular bike to an ebike tend to favor PAS bikes since pedaling is what they are used to and what seems normal while riding a bike. Bikes with throttles, particular those that can exceed 20 mph really are different from regular bikes or speed limited PAS bikes. Obviously, a regular bike or PAS bike can exceed 20 mph, but the rider or gravity has to provide the ability to do so. In my many years of riding, I've found very few recreational riders (other than those in a paceline) who can exceed 20 mph for any substantial distance other than down a big hill.
I don't think there is anything wrong with throttles. They are particularly useful for folks that need them or who are unfamiliar with the shifting required on a PAS bike, but I'm not surprised that bikes with throttles (or a speed limiter of 28 mph) are placed in a separate legal classification in some jurisdictions.
My guess is that the California classification system is likely to be adopted nationally over the next 10 years or so as ebikes become more prevalent. And think that is a good thing for all stakeholders in cycling world, whether they use an ebike or not, from a safety point of view.
In my opinion, to claim that a throttle equipped bike that can exceed 25 or 30 mph, should be treated the same as regular bike or a speed limited PAS bike on anything other than a public street ignores the reality that while public streets are built for higher speed traffic, MUP, bike trails, single track, etc are simply not. Having someone whizz by a walker, a little kid on a bike or another cyclist at 30 mph on a bike path is, in my opinion, simply unsafe. A throttle makes it easier maintain higher speeds for longer distances, which is the essence of the safety issue.