Studies of silicon qubits are developing into a major research focus , due to their inherent long electron decoherence times. However, the presence of the additional valley degree of freedom (VDOF) introduces a higher degree of complexity (compared to cases where the VDOF is absent, e.g., GaAs nanodevices ) which has not as yet been satisfactorily deciphered, experimentally or theoretically. Indeed, a number of publications consider it as a challenge to be overcome or to do away with (see, e.g., Refs. ), whereas a second group of publications (see, e.g., Refs. ) considers it as a potential resource to be further explored. Experimental eorts in both directions are intensely pursued, but a denitive resolution has not been reached as yet.