No contradiction at all. This comment indicates the common misconception...perfectly...The steel's spring rate has NOTHING to do with its strength. It's two different things.

That is the hardest concept to "get". They all have the same reaction in the elastic region. They all go up the same path on the Stress vs. Strain graph. It's just that high strength steels keep going up at the same angle, while low strength steels go nearly horizontal way below, depending on their yield strengths.

And THAT is the real reason why there needs to be all kinds of different strength steels. It's how highly it can be stressed before it plastically (permanently) deforms.

Note the graph with curves for different kinds of steels used in industry.

R.