I'm guessing they prefer the Hitachi IGBTs fitted to the /0 and /1 over the Alstom GTOs that the /2 and /9 have. Unless they want the Brush GTOs the BREL units had when new before they were IGBTed around 2011 For those that don't know the 465 is really two different trains from different builders (BR had a dual sourcing policy at the time) - they have surprisingly little in common despite a similar overall look.
I don't think the /9 is horrible but I would like to see the 465/0, 1 and 466. I think they could do something similar to Armstrong powerhouse where if you already own the 465/9 you get it heavily discounted and maybe even a free download, and if you don't already own it you get all 3 for the price of 1.