[Plus there aren't four shifts a day considering the One is produced by the News channel and frequently uses its presenters, as does Victoria Derbyshire (which people on here frequently forget is a News Channel commission, not BBC Two). Ben could even have taken over Chris' slot at weekends (he has presumably taken over some of Chris' OB duties) yet Gavin Esler seems to have taken it instead.
For what it's worth I'm not a fan of Ben as a presenter, and don't think the schedules have been nearly as strong post-TVC (save for Martine Croxall).
I wouldn't get hung up on the precise numbers of shifts.
The Victoria Derbyshire programme situation is (hopefully for Victoria) a temporary one, so I'm not really including that. Also the News at One presenting roster is affected by George Alagiah's illness.
The reality is that in terms of the News Channel:
One double headed morning shift has been removed, and the second extended and cut to one presenter
One evening shift has been removed and the second extended.
That's four presenting rosters removed during the week.
At weekends one shift has been removed on both Saturday and Sunday (which is effectively Chris Eakin's old shift).
With all those changes there are bound to be changes in individual roles, but I wouldn't necessarily see them as demotions.