"dynamic nature of proteins is widely accepted, the fact that structural heterogeneity manifests regularly in experimental structures — those in the Protein Data Bank (PDB) today — appears underappreciated" I think this is largely true. For non-structural biologists its just not the first thought.

"techniques average over an ensemble of many molecules... These averages are blurred by the structural differences from molecule to molecule, requiring models that incorporate structural heterogeneity to explain the data" A big hurtle is just amount of data needed / how to show heterogeneity