My old Bose 601s don't have any low frequency attenuation on the 8" woofers. But their voice coils melt long before an M3 starts sounding bad.
I would not be worried about your M60 mid under distortion. I'd be more worried about the tweeter.
As for how, it's all about the surround and spider materials and geometry,the adhesive used to couple them to the driver, the adhesive used on the voice coil, dissipating heat through the aluminum dust cap, and aluminum tweeter faceplate and cooling the voice coil hot air through vents.
Note your M60ti don't have many of the improvements above which lead to greater linearity at higher volumes and greater longevity.
