Drumlins geomorphic differences are tied to different architectural compositions.

Drumlins over crystalline basement areas are of the rock-cored type with sediment emplacement around a seeding rock core.

Drumlins over Palaeozoic sedimentary rock strata with deep Quaternary drift on top are of soft-cored type.

The latter are formed from compressional constructive deformation, accompanied by excavational deformation.

Drumlin formation is better explained by a set of processes where equifinality is playing a significant role.