Although we are not privy to the detail of CS’s thinking, it seems they have opted for a linked Mk5 sleeper/ class 92 deal so they have access to models of the whole train which they can possibly market in some form in the future. They may have needed confidence that they would have a high spec 92 for that to work for them.
On the plus side the prematurely announced Accurascale/RevolutioN trains announcement has prompted DJM to make two announcements on the Class 92 00 gauge project in a couple of days. Keeping momentum on the Class 92, and possibly attracting more crowdfunders with some spirited marketing, are probably the best routes to delivering the locomotives viably.