Not sure if this is necessarily a fix for the cracks. Really seems that they are working the newer propulsion system motors into the phantom line. There is supposed to be a reduction in cogging with these which may help reduce wear on the chassis but I doubt this was specific for the cracks.
Doesn't it look like there is more surface area of the new motor in contact with the shell? That in itself would seem to act as a big washer thus giving a stronger support to the shell.