Are you sure about that "no Mach trim" statement? The NTSb report on the Egyptair B767 specifically mentions Mach trim in its discussion of the pitch axis controls....
The 767 autoflight systems include the autopilot/flight director, yaw damper, automatic stabilizer trim, Mach trim, maintenance monitoring, instrument landing system deviation monitor, and thrust management systems. The thrust management system includes autothrottle control.