Buzz Box
Were the FMAs you quote for the 777?
Worth noting re. the 47 that you do NOT get an 'IDLE' FMA during a FL CH descent. The sequence is THR, until the levers are fully closed, then HOLD.
'IDLE' is a specific computed thrust level which the FMC can compute - FL CH can't do this.
The 2 minute function is part of the computation for FL CH which is most useful in providing for a non-overshoot capture of selected altitude. As the altitude is approached the Pitch/Power input will be progressively modified to allow this.