This is pretty interesting to come across. We are UK Product Designers at Flynn and we tend to see the term evolving more so over the pond to refer as you have covered digital / software product development, as opposed to the research design development of largely physical products.

I can see you set out to clear up the confusion, not an easy challenge as it benefits in many ways from not having harshly defined boundaries. We think product design is more a way of thinking which can be applied in many cases to sytems and digitaly. In some ways it is the concept of design thinking where the creative DNA of the entity in question has to be fully considered to survive when scaled up, be that via software chanels or full mass production in factories. Small tweaks in the DNA have a massive impact to the parent organisation.