z9 BC GA2 announcement and CBU

In my post on the z9 BC GA2 announcement, I put some exclamation marks after the CBU item stating that "the z9 BC Model R07 will allow CBU to all S07 capacity settings".
In fact this is important, as there had been some kind of break with the z890 CBU settings. Up to the z890, the CBU had always been a full engine issue. So if you had e.g. a z890-260 (390 mips) as production machine and you wanted to buy a machine in cold standby with CBU, you could buy a z890-110 (the smallest z890 with 26 mips) with one CBU. When the CBU was activated, the z890-110 engine and the CBU were set to full capacity giving you a z890-270. You can find a detailed explanation in the redbook 'IBM eServer zSeries 890 Technical Introduction'. This was an affordable DR solution.
Z9 BC broke in two ways with this possibility. CBU was no longer a full engine thing as you can now order CBU up to a certain capacity. I guess anyone can live with that. There was however also a split of the z9 BC into two models : the R07 and the S07. And it was impossible to buy the smallest R07 (R07-A01 with 26 mips) and have a CBU capacity for a S07. Similar to our z890-260 example, the same customer would now have a z9 BC S07 N04 (409 mips). So as opposed to the z890, you could no longer buy the smallest z9 BC machine which meant a much larger investment for the customer. The lowest possible model in this case was the smallest S07, the S07 R01 with 193 mips.
So this limitation has now been lifted. The redbook (draft) 'IBM System z9 Business Class Technical Introduction' has already been modified accordingly.