after G/A you get something like 3000 ft/min or even more.
If i want to stop at 4000 ft and level off at this altitude with that rate of climb i would need to start levelling off several hundreds of feet before 4000.
if i do that without the possibility to retard the throttles (because flaps are still extended) the aircraft will accelerate and i'll meet the flaps retraction speed before being stable at 4000 ft.
Meeting flaps retraction speeds i'm then forced to call BUG UP before reaching 4000 ft.
as you can see i'm breaking the rule "Mantain F15 until levelling off". That is what i was asking for and it's not really a problem for me.
mo hai capito ?