DF linearization conjecture for Goursat bundles not ESFT-equivalent to Brunovský normal form

Let a control system with at least two controls be a Goursat bundle, and suppose it cannot be transformed to Brunovský normal form via an ESFT. DF linearization conjecture. The control system has a DF linearization. This conjecture proposes DF linearizability as an alternative when ESFT reduction to Brunovský normal form is impossible; the source reports it as an observation-based conjecture, with no resolution given.