# Why is buckling said to be independent of material strength?

In many sources, such as here, it is said that buckling failure is independent of the material's strength.

But in many building codes, yield stress of the material is a factor that changes the allowed buckling load. The Perry-Robertson formula for example, which is the basis for buckling curves in Eurocode has yield stress as a parameter. The formula is derived by assuming initial curvature on a beam and solving for the allowed load so that yield stress is not reached in the cross section of the beam. So clearly yield stress affects the magnitude of allowed load against buckling. So why is it correct to say that buckling has nothing to do with yielding?