No that is not what i said

Of course it depends of the lenght of the effort.
3km @ 5% are easier cause you are riding shorter then on 9% gradient of 3km.
Going all out for 10 minutes on a 5% climb is just as hard as 10minutes all out ona a 9% gradient, no difference there.
However, the steeper climbs are, the more difficult it gets for riders to reach their normal watt/kilo ratio.  The heavier a rider is, the more heavier it gets to reach the flat line watt/Kilo ratio. Hence lighter riders have an increasing advantage the longer and steeper a climb is.
This does not mean that the climb gets harder, though. You still push at 100% but your power output production is going down. Hence you go slower, but it doesn'T feel harder then psuhing 100% in the flat.
You can't push more then 100%. Neither at 0% or ad 100% gradient.