Used to work there many years ago, but remaining anonymous....
XIV has been a thorn in DS8000's side ever since it came into IBM. The DS8000 lot are old-shool IBMers who didn't like this upstart, and XIV was starved of funding, so most of the people who came in with XIV left the company. DS8000 props up the mainframe business, so it's never going to to go as long as they sell Z, so XIV was starved out. They took the look and feel of the XIV GUI and applied it to the rest of the storage range (which badly needed it) but the rest of the XIV code didn't fit into the legacy architectures of the older DS8000 and SVC-based stuff. It did fit with the flashsystem though, as it needed things like copy services, hence the A9000.