Anybody who knows what "dhd build" means?
Maybe this means that the DRM keys will survive the flashing to SFOS, and will still be there if re-flashed to Android? I'm also guessing that implementing Sony's software enhancements to the camera in a future release of SFOS X will depend on access to those keys from SFOS, if not directly, then from some binary blob from Sony. Like you I have an Xperia X waiting for the release, but bought second-hand so already on Android 7. I'm going to hold off on downgrading to Android 6 and extracting the DRM keys until I know whether it is really going to be necessary.