Due to timing the controller uses 2 MC68k processors on the same chip.
Which were only mfg for NASA for this task.
So probably run out of chips.
The RS25 was one of the jewels of the Shuttle programme. There were a fair few mods that could have made it both higher T/W and more reliable. Using it in expendable mode is deeply stupid. Hopefully this time round they will use actual off the shelf chips.
Since it will operate no further than LEO they don't really need to be space rated either.