I don't know, I chose and ordered D2 because of the features. The question can probably be answered by comparing the possibilities/performance, if there is a technical difference at all, it could also be commercially justified.
I did a lot of research to find a smartwatch with reliable blood pressure measurement. The D2 for 310.00 is medically certified and its measurement results are accurate. The Italian term Orologio actually just means watch. I assume that it is the same watch.