Hi Stefan,
Great article! I have been working on Delivery Optimization implementation now for 2 months. We have the scenario of a VPN client that is NOT detected by DO.
So the statement "In VPN scenarios the Delivery Optimization Downloader is still downloading the content, but not sharing content with peers" only applies if the DO cloud service recognizes your VPN client, as stated here: https://docs.microsoft.com/en-us/windows/deployment/update/waas-delivery-optimization#how-does-delivery-optimization-handle-vpns ?
Helas, there is no documentation or blog available on what DO behavior is on non-supported VPN clients: does it suspend P2P, does it suspend downloads/uploads? etc. However I am hopeful that this scenario will be covered in the doc soon or that DO will evolve to also take other VPN clients onto account.
Regards,
Johan