Alex
Agreed, I also think it highly implausible the disconnect was due to reaching trim limits.
It is clear though that flying level at 134kt would result in a very nose trimmed up condition. When the a/p disconnected (for whatever reason), if the immediate reaction was to apply full power (without first lowering the nose) then a stall could easily have resulted. Couple the pitch effect of applying power with the sudden short term increase in airspeed when already at such high alpha....