My guess is cost. the ESC looks identical to MMP, no doubt, but the motor... I am not sure Patrick makes it. HPI might has found a more inexpensive Chinese motor with okay performance.
The ESC is a Mamba Max Pro, HPI special version.
The motor is a low-cost version 1517. (a few changes from the standard version to make it much lower cost to produce.)
Patrick del Castillo
President, Principle Engineer
Castle Creations