Well, I know of no such law, never heard of a torque law.
It is not uncommon for induction motors here to have all six ends of the stator windings brought out for Y-D starting. But three phase LV is (almost) always 400V* so dual voltage operation is rarely a requirement.
*It is now nominally 400V in UK. The nominal voltage was changed from 415/240V to 400/230V to harmonise with the rest of the EU and their nominal 380/220V was increased to 400/230V. All a bit of a fudge, really.