Originally Posted by
Atlas Shrugged
A37575, you have to remember that there is very little, if any, reverse thrust. Most reversers only affect the fan air, not the flow from the core. Whilst the fan flow might generate some reverse, the core is still pushing you along.
Almost all of the thrust generated by a large turbofan comes from the fan, so it's illogical to suggest that the absence of a core reverser makes much difference.
Early RB211s, for example, had both but the core reverser was subsequently deleted because it was a PITA for very little benefit.