i know the dmwdave referred to in the linked article, and Ive heard his account of these PG devices. He holds some records at MtCotton Hillclimb here in a couple of classes with his Swift. They do work OK with lower powered cars. But when he turboed his swift engine, the device was totally ineffective and he reverted to a locked diff (yes in a fwd).

It can't possibly act as a locker, but it can provide a LSD action.

All diffs (except detroit lockers) always provide a 50/50 torque split between both axles - even open centres. In an open centre, when one wheel looses traction, it limits the amount of torque the engine produces (equal and opposite forces and all that...). Both wheels are still getting the same torque applied to them, but its not enough to do any really useful work through the wheel that still has traction.

what LSDs do is artificially add resistance to a wheel loosing traction to increase the amount of torque the engine can produce and apply to the ground., so that some useful work can still be done to drive the car forward.

locked diffs (welded) provide a 50/50 torque split too, but their limiting factor is the wheel with the most available grip.