Performed according specification
The Autopilot was in command and it performed the maneuver that it announced through the FMA.
The active mode was ALT CAP, which is a precalculated path from climb conditions to level flight conditions.
The capture was initiated far below the level off altitude, because of the very high climb rate. During the execution of the capture, thrust was reduced from T/O thrust to CLB thrust, this resulted in too little thrust for the remainder of the capture maneuver.
The situation resembles very much this case (Canada TSB)
Aviation Investigation Report
Aircraft Pitch-Up/Stall Warning on Departure
Air Canada
Boeing 767–233 C–GAUE
Toronto/Lester B. Pearson International Airport
Toronto, Ontario
26 January 2004
Report Number A04O0020