I never suggested it was. It's primarily a commuter railway however since the Evergreen projects it became a viable alternative to people travelling from Birmingham to London, with 100mph trains making the journey in little over 90 minutes although of course that is now a distant memory.
With Evergreen the idea was travelling between London and Birmingham with no noticeable time difference against Virgin to attract a broader range of time sensitive customers, but with Chiltern having much lower costs and therefore lower fares. I've no idea why the current management stepped back from it, they were making good money from it.
The Chiltern Mk3s were supposed to be standard class only with a trolley service, but they had to use the WSMR ones when DB refused to fund refurbishing more Mk3s for Chiltern. Ironically Chiltern only bought Mk3s because the ROSCOs didn't have any suitable trains and the manufacturers wouldn't make any due to changing emissions laws (or something like that as I recall).
There's quite a few options for Chiltern:
EMR's Class 222's are about to be replaced, 23 5 car sets
Avanti's Class 221 are about to be replaced, 18 5 car sets
Class 180s, you can knock together 11 5 cars formations
Mk5a: 13 5 car sets
My feeling is that the note about "less noise" means they don't want the Mk5a. The Class 168s are DOO South of Banbury, which saved a lot of money, I wonder what the plan is from that aspect?