L337,
You offer some interesting observations but if you think them through you would see the following;
A/C climb rate = 100fpm
Altitude climbed above desired = 200 - 300ft
Time to achieve this = 2 - 3 minutes
Time to descend back down to desired alt. = 2 - 3 minutes
Total time to establish cruise airspeed, approx 5 minutes
I would suspect that if you had just leveled at desired altitude and waited 5 minutes the speed achieved would have been the same.
Of course, I wasn't there to witness any of this but I also doubt anyone has ever been able to show results for the two methods using the exact same aircraft at the exact same gross weight at the same altitude and OAT. If someone has managed to do this and in each case started their stopwatches the moment the aircraft first reaches cruise altitude and stopped them when the aircraft reached desired cruise airspeed I think they would find that the conventional level off would be slightly better.