Interestingly, the AudioControl X9 has a firmware of 1.29 whereas the JBL and Arcam are at 1.28. The JBL/Arcam are 4/28/2020 and the Audiocontrol is 4/29/2020 so it suggests that AudioControl is doing *something* extra.
The firmware on these are in 2 parts. The OS called bit image.swu which does streaming, control and lots of other bits (Like receiving the data from Dirac) and the DSP firmware which does the most of the low level essentials. The image.swu in the Audiocontrol is identical, I suspect the difference in the X7 fw file is to allow for the two extra XLR inputs but there could be other differences.
When I recovered my AV40 over SSH from a bad flash it gave near root access to the OS. The scripts reference the one minor version difference of the Audiocontrols as part of the same update bundle so I suspect they are developed in tandem but Audiocontrol certainly decide when to release firmware for the X series and have so far been more cautious than Arcam and JBL.