<You do occasionally see them some 20 miles from the airport still under full power and very low.>
We're talking about something different- climbout now! PIA will be heavily loaded in an older 747. Being low is not dangerous! The performance will all have been calculated, and if evidently dangerous, you can be assured ATC will pick up on it. But we're seeing an innocent airline accused of something serious here and such unfounded accusations should not continue. I've taken off from Dharan in a fully loaded old 747 with original early model engines (-3A) in high desert temperatures (the much 'loved' G-PZ). Nosing down at 1500' in a temperature inversion to accelerate for flap retraction (and drag reduction), it wouldn't speed up. We blasted across a large part of eastern Saudi trying to get going with incredibly gradual acceleration. Not a problem. Should you lose an engine, there is an on-the-ball F/E and fuel jettison system. Over the English countryside, even in such a low powered early model, it is all allowed for in the performance. But 'very low 20 miles out'? I don't think so. More ATC than anything else.