Think you might find that research shows width is a much more contributing factor to being able to sleep in economy. 

but will have a narrower seat due to 10 across seating as opposed to 9 across on the 350

The seat itself looks an excellent design and the extra 1" of pitch is great. However the measurement of seat width is misleading as it's taken between the inside of the armrests and this means that by reducing the thickness of the armrest you make the measured width of the sest bigger. It is in ...

These 'throne' seats can also be 'coffin' seats as you are crammed in on both sides at shoulder level by the leg area of the seats behind so I'd actually avoid these seats personally and go for 1A, 3A or 5A with the extra shoulder room created by the armrest going down.

If they bought the aircraft at 2005 prices when it was an 8 across in economy aircraft then why wouldn't they operate it as such? If they don't then I fear yet again they will have bought the wrong aircraft again, this time buying Boeing when it should have been last time.