Hmmm, what's that? You say Manet wasn't really an Impressionist? Okay, you have a point. But of course, Degas and Caillebotte were surely Impressionists with a capitol "I." And they used black a lot.
Okay, okay. You're right. They used black when painting people and manmade things like buildings and hardwood floors, stockbrokers and ballerinas. Perhaps, as you say, black for these kinds of things would be a special exception to any rule.
But Monet, Claude Monet, the primo Impressionist, sometimes used black as well and used it for landscapes! Ah yes, though many beautiful Impressionist landscapes haven't a stroke of black, others surely do.
Lots of my landscapes haven't any black either; but some do, like Junk Trees above. It's a 12x9 plein air of a much-maligned species, the hackberry tree. Hackberries grow fast and grow just about everywhere in Middle Tennessee. They're not "good" for anything like building or burning so they only rate as junk, though beautiful junk.