A lot of people have missed that the existing six cars carry a lot of standing load. The layout changes aren't particularly important for that as what's lost in narrower doors will partly be made up for in removing the step at some stations.
What is a problem is the loss of a whole vehicle given the increase in seating is ~0. So all of the extra capacity is riding on the one extra fast train between Leeds and Manchester (provisionally a Hull - Manchester Piccadilly).
TRU specced for 7*26 m or 8* 24 m sets. A 5* 24 m would be foul of various crossovers in a pair. Even on today's traffic levels 5*24 m would run heavily loaded with standees so one extra train per hour is doing a LOT of work on forecast in eight years time.
It does rather look as though the large extra costs for batteries and charging at outstations has caused them to run out of money and spec to five vehicles per set rather than six. It proves once again that any savings of opex from going from DMU to battery are illusory, except for short, low speed routes.
By contrast the extra cost of speed above 110 would never have been justified for these units. TRU are only lifting permissible speed above this between Church Fenton and Colton Jn, so York - Church Fenton would be the only short section they could regularly run above 110, plus whatever very limited occasions they may run non-stop through Thirsk.