I feel like the real motivation behind this is that far too many people believe that the hard part of getting solar panels adopted is in finding places to put them. So this law "solves" the problem. But that's never been the real problem. It's arguing about the color of the bike shed when the real mover of solar panels is price and output. Price isn't addressed here and you should expect installing it everywhere will lower the average output of installed panels (since it'll be put on non-optimal shady locations too).
I think this just falls under 'practical politics.' It's a revenue-neutral tax on a relatively wealthy demographic. Politicians get to be associated with something perceived as good by their voters.
I don't think a deeper analysis is required. Anything that meets those requirements will also be passed.
I haven't been able to locate the specifics of the bill, but my expectation would be that the regulation doesn't apply if there isn't sufficient sun exposure or rooftop area to justify the solar installation.
