Following up on my own point, I found this quote on a Shimano's website: "We promote health and happiness through the enjoyment of nature and the world around us."
It seems that they find class 1 e-bikes more in line with that philosophy than class 2 or class 3. Agree or disagree with them (I ride class 3 to enjoy the outdoors, so I disagree), but that seems to be their approach.