SFD-1001 repair attempt, round n+1

Thanks to a tip I got on plus/4 world I've tried to get some spares for my SFD-1001.
According to the tip I can buy Rockwell 6530s on eBay. This time I was more careful, I did not order three of them. It arrived very soon and yesterday I took an attempt at the repair.
Of course this does not work either. :( However I started to test with component swapping to determinate if this is the true problem and found that fortunately it's not. One of the 6502s is gone "only" but this can be found more easily. :) Well I needed to recognize that this drive (in contrast with the other two) has a different flash-error code.
But I'm still interested that why does the type of the 6530 matter for these drives. They are in an adapter so their ROM part is disabled and there are no other differences between different RRIOTs. :O