Why not just use max reduction for takeoff and then full CLB after flaps up, or after flap retraction is initiated? Best of both worlds.
This consideration (and ramifications) has been around since flex was first introduced.
One of the first operators to play with flex was Qantas, back in Wal Stack's day as Ops Eng boss. I can recall his tale when one of the early flights had the crew coming back with the complaint that they had to push the throttles up to climb power at the end of the takeoff sequence .. he changed the regime then so that flex didn't go lower than climb.
At the end of the day, it is up to the operator, subject to engine contractual requirements, to figure how the engine ought to be operated .. as with tdracer's example, some go all out .. while the majority are a bit more dollar pragmatic.