If BBN's scenario holds water... (I am only conversant with the T56 in this regard which had it's very own set of weird prop issues with the HS) then there would be a bit of an issue brewing...
BUt... I am missing something in BBN's rationale; if the power levers are retarded, then the blade pitch will fine until achieving the FFPS, at which point it will result in an under speed condition that is countered by fuel scheduling, ie it becomes a minimum thrust condition. ( it is not uncommon for various TP's to have cases where a rapid power lever closure will result in a momentary increase in thrust at part of the operation). The blade at all times is free to increase pitch without any limitation, up towards feather. The FCU/Prop Gov must indeed be unusual.
§ 25.33 Propeller speed and pitch limits.
(a) The propeller speed and pitch must be limited to values that will ensure—
(1) Safe operation under normal operating conditions; and
(2) Compliance with the performance requirements of §§25.101 through 25.125.
(b) There must be a propeller speed limiting means at the governor. It must limit the maximum possible governed engine speed to a value not exceeding the maximum allowable r.p.m.
(c) The means used to limit the low pitch position of the propeller blades must be set so that the engine does not exceed 103 percent of the maximum allowable engine rpm or 99 percent of an approved maximum overspeed, whichever is greater, with—
(1) The propeller blades at the low pitch limit and governor inoperative;
(2) The airplane stationary under standard atmospheric conditions with no wind; and
(3) The engines operating at the takeoff manifold pressure limit for reciprocating engine powered airplanes or the maximum takeoff torque limit for turbopropeller engine-powered airplanes.