You're wrong. Photostream does not download the source file. It downloads a preview. It dynamically loads the source file as you view individual images.
Second, I never claimed that photostream was intended for sharing amongst others. It was promoted for sharing amongst your devices. That isn't the issue. The issue is the removal of the distinction between photostream/Cloud Drive and local. Apple wants you to see them as one in the same. THAT'S the central problem.
See, these basic gaps in your understanding of how it works are why it's kind of pointless to continue discussing it with you.
Second, I never claimed that photostream was intended for sharing amongst others. It was promoted for sharing amongst your devices. That isn't the issue. The issue is the removal of the distinction between photostream/Cloud Drive and local. Apple wants you to see them as one in the same. THAT'S the central problem.
See, these basic gaps in your understanding of how it works are why it's kind of pointless to continue discussing it with you.