At 65 knots, the autothrottle enters a hold mode ('goes to sleep') - the throttle position will remain fixed, the EPR trim (small adjustments to EPR command intended to line up EPR across the wing to account for slight throttle stagger), and the bleed debits are held constant - this is done to prevent a single failure (the FMC/Autothrottle) from affecting the thrust on multiple engines during a critical flight phase.
What the FAFC does is fundamentally different - it enters a "lock and lapse" mode, meaning it follows a fixed EPR lapse rate with speed and altitude (regardless of changes to TAT). It will continued to close on EPR Command, even if EPR actual has not lined up with EPR Command when it enters 'lock and lapse".
If you move the throttle by less than 2 degrees (memory says it's 2 degrees, not 3 degrees, that unlocks), the 'baseline' EPR command will change, to reflect the new throttle position, but it will retain the lock and lapse characteristics - just from a different baseline EPR. IF you move the throttle by more than that, the FAFC will exit lock and lapse and just control normally based on the throttle and ambient conditions.
Clear?