Hi Bram,
Thanks for sharing. You really touched many of the pain points with dealing with product people that have not been trained properly to work in a software development environment.
Sadly, after decades, the last part "they figure out eventually..." I did not see that, unless some few special cases. Somehow, product people tend to create very isolated and protected environments so they can live in their bubble and blame developers.
I would love to see some of your whiteboard sessions :-) I am quite sure that I have a lot to learn there.