This is a different issue than the HDCP issue. What your issue is is that the component outputs are not live while HDMI is in use. However that's a great idea, and could be helpful for others with issues similar to yours.
It has something to do with HDCP (or copy protection) because the problem is only on the HBO channels. But, you may be right that there is a subtle difference.
With the 612 to the TV and the Sling on component, HBO (on Sling thru component) is fine if the TV is on. I get the Copy protect message if the TV is off (no HDCP Link?). If I unplug the HDMI cable (or switch the HDMI switch away from the TV), the Component Comes Back.