I believe the difference is this:

When the engine cuts the fuel or timing the engine can not make any more power, thus limiting the engine's ability to rev any higher. When you are redlining in 3rd and shift accidently to 2nd, the engine speed becomes tied to rpm of the drive line. This forces the engine to spin as outrageous rpms without respect for timing and fuel cut off. the drive line is forcing your engine to spin fast enough to hit 90 mph in second gear.

These are just my thought.