What about the Trimmable Horizontal Stabiliser? Calling it "Trim" is misleading. As it cranks in Nose Up, it is fundamentally changing the Angle of Incidence of the Stabiliser, not its trim. Any deviation from neutral Angle of Incidence changes the neutral point of the Stabiliser and its ability to provide a consistent downforce. In short, the character of the maneuverability of the airframe in Pitch is altered, imparting a stubborn bias to the Pitch control. At full THS Nose Up, the aircraft cannot alter its Pitch away from Full Nose Up, the elevators are essentially useless.
Oh it is trim all right. Trim refers to the effect on the aircraft as a whole, and is used to control the aircraft pitching moment within the limits of its trim authority.
There are any number of aircraft that use this method of trim. Virtually every airliner in use today trims the horizontal stabilizer angle of incidence. Many Piper aircraft trim in this manner, as well as a number of military aircraft.
The thing that did not make sense about AF447 trim behavior was why was it possible for the aircraft to continue trimming nose up (In Alternate Law) after reaching stall AOA?