Waveman - as far as I'm aware Flybe is the only 400 operator that recommends flap 35 landings as the standard, and this is due to the larger proportion of shorter runways on the their network.
I think you'll find that it's more to do with a historical incident from the early days of the operation involving a tail strike at flap 15.
Well handled evacuation though from this incident. Would be intrigued to know if they used both sets of doors on the LHS. Not easy to tell from the video, but the rear left exit seemed to be slightly lower to the ground than on a 'normal' landing.