OK, I'll go with the Challenger 605 since it is one of the types I am current on, and the other - the CJ - is not a Part 25 aircraft so really doesn't qualify for this discussion.
So let's start with the AFM.
All it says in the normal procedures section is the After Takeoff Checklist where it just says:
O. After Take-Off Check
(1) LDG GEAR lever .............UP
(2) FLAPS ................. Set to 0°
(3)
No mention of heights or speeds.
In the FCOM1, expanded normal procedures, it says:
G. After Take-Off Check
(1) Landing gear ........................................................Chec k retracted.
NOTE
During normal operations, landing gear and flap indications are normally occulted (removed
from EICAS) when the landing gear are stowed and the flaps are up.
At not less than VFTO + 5 KIAS:
(2) Flaps....................................................... .................. Set to 0°.
(3)
Note it says "not less than".
Also bear in mind that this is the checklist, which is intended to be used as a follow up after the event. The after takeoff checklist should not normally be read until the aircraft is well away from the airport since before that the crew should be concentrating on flying.
So flying a NADP profile in no way conflicts with the AFM, ensures obstacle clearance in the event of an engine failure and gives commonality of procedures between normal and OEI.
As I said before, the height trigger is to start acceleration and is only indirectly linked to flap retraction, and certainly should not be as low as 400ft.
In fact it is the rush to pull the flaps up quickly after takeoff which
came out of the mists of time as tribal-knowledge and has no place in modern ops.
Part of the problem is that training providers (I will not single out FSI since there are plenty of others) market themselves as teaching people all they need to know, and most pilots do not make the effort to find out how little the actually know.
A challenge for you all - how many of you have actually read the AFM and the FCOM (or equivalent) from cover to cover? You might be surprised at how much you find in there that is not as you were told in training - even on a factory course!