I wonder
now mind you I'm a pilot and not an engineer...but the lower bypass engines like the JT8D by Pratt and Whitney were routinely used to back up on the ground *power back procedures.
the newer high bypass engines aren't.
so...I'm thinking that when used in earnest, the older engines reverse capabilities might have been a bit better than the more efficent higher or ultra high bypass engines.
and to me, landing a 757 on a 5700 foot runway at sea level (orange county calif) is much easier than landing the same plane at a 6300 foot runway at over 6000 feet elevation.