I still don't know if BC mode on XSX|XSS means the CPU runs at 3.6, 3.8, or developer's choice, and how much that alters the thermals of the console.
Very good point. From the earlier comments from Xbox Engineering, I think the default for BC would be with disabled SMT and running at the higher CPU. This is from an assumption that older titles were developed around Jaguar cores so the game code would not have dynamic threaded subsystems, so slightly higher clock would win out over SMT-enabled from performance perspective.
It's unknown if any of the following are possible, but they don't seem improbable:
- XDKGen9Aware allows developers to specify behavior on Gen9 systems
- Xbox Firmware allows for title specific profile behavior overrides for any given Xbox One BC titles