Mostly this is correct. Few exceptions -

Weather patterns on East coast can be unpredictable, much more so than central valley CA. torrential rain = mud leading to bogged down equipment, this can be the difference between a profitable job and unmitigated disaster for an installer.

Second, construction cycles in utility solar can be a bit wonky because of ITC tax credits, lots of turnkey providers looking to have construction starts in q4.

Nah solar installations work across all weather categories. You just have to manage adverse weather (i.e. additional costs). Some climates have better solar production others have higher costs of energy which solar can undermine.

But they work the most efficient in mainly sunny and arid areas, which is why it might make sense, to focus automatic constraction there and then later also adopt to more harsh conditions.