So actually using a service frequently and knowing full well what demand is like as a result of that experience does not count for anything here these days...
Evidence does not have to mean "verifiable external sources" so far as I'm concerned, but accounts of a single journey are not exactly compelling evidence, never mind a business case for 10-car IETs.
Or are you about to demonstrate you use the 16.22 all the time and on-board conditions are actually always the way you described on the previous page? As opposed to the way I know they really are, as someone who does frequently use that specific service.
Why should anyone believe any claims you may make about passenger numbers on services around Manchester, since you have now declared that such personal experience is irrelevant?
One of these days perhaps someone will provide compelling evidence to demonstrate why a GWR IET fleet almost entirely made up of long single-unit formations, whether of nine or 10 coaches, is what is required, but I won't be holding my breath.
Having seen the - being generous - modest number of people on board the first nine-car GWR IET returning to London while working the 17.25 from Worcester earlier this evening, I know for sure that is one service that does not need to be worked by a unit with anything like 640 seats, which is why it won't be in the normal course of things.
You may have a point about 387s - or you may not. We don't know quite what the 769s will be doing long term, which may well include things some 387s are doing right now. There were plenty of other factors at play when it came to the HEx deal, such as avoiding big bills to build a new depot for the 332s, plus a 387 top-up for GWR could be on the cards in 2021 when c2c releases the sets it is using until its Aventras are delivered, as those 387s came from the same batch as the GWR fleet.
There was disquiet within GWR about losing known quantities, in the shape of 387s and Turbos, for 769s. And no, you won't be getting a verified external source for that, as I know it from private conversations with people inside GWR.