OK I’ll word it differently. When in an Activity and switching directly to another Activity mine does NOT do that, it only sends the Off sequence to the Devices no longer needed. I have change HDMI in my TV shutdown sequence and it only ever does this if the TV is not in the next Activity, it would also turn my TV Off and back On again (it’s a toggle) if it did. I would double check your settings as it should not do what you are seeing.