It's not exactly whizzing around at light speed in the way that you imagine if it's beneath an event horizon. The entire point of an event horizon is that everything beyond it physically cannot move outward. The horizon isn't some kind of physical barrier, it is just the farthest distance at which the black hole's gravity becomes inescapable, that doesn't stop applying just because you've moved past the horizon, and in fact it only becomes more true.

If you imagine any sphere beneath the event horizon which is centered on the singularity, that sphere is just as inescapable as the farthest such sphere which we call the event horizon.

Additionally, the event horizon is inescapable to everything. Even gravitation is transmitted at the speed of light, and cannot outrun the cascade of inwardly falling spacetime beneath the event horizon. So no possible change in the distribution of mass within a black hole could have any effect on the configuration of spacetime at the event horizon, or even on any spacetime further from the singularity than itself.