We can imagine that, at a certain regime we can eventually meet a condition where the stepper motor is at its maximum opening and cannot provide more fuel...
I think the remark we can find in S76C+ RFM (page 1-5 part 1 operating limitations - "Gross weight reduction due to maximum fuel flow rate restriction" ) is reflecting this condition.
But it seems that, given the rather low temperatures and pres. altitudes where this limitation is in force the limiting factor, here, will be the torque ( 135%) before the N1.
I usually fly the "C+" between a ISO +10 and ISO +20 temperature conditions and never had to deal with this limitation untill now.