I received some more information about this. Please see my report below.
What: In Win10, CUI scaling options are shown based on the current resolution. The UX (user experience) improvement previously implemented in Win7/8/8.1 to show all the scaling options independent of the current resolution is not yet complete for Win10.
Why: Win10 has different ways to implement this feature than previous OS and we are currently working with MSFT to mitigate user experience issues or broken functionality. This includes investigation into requirements and discussions on improvements.
When: This is a complex task with top priority, work is in progress. Honestly, I know it will not be enabled by OS launch, though the development team is targeting my next status update for July 31st.