It suddenly started in 1911, when the deep profile portrait of GV came in. For comparison, the portrait of Ed8 is sufficiently shallower that ghosting is less pronounced and Britannia suffers much less. As the ghosting was an accidental effect, it is neither intentional nor invariable so there are good strikes out there, but they're hard to get hold of.
As for the poor hair detail on some, that's purely down to the overuse of dies - note how the increase in penny mintages was sharp and dramatic, and "there was a war on" too. Bear in mind that the obverse 'sucked' metal from the reverse even when the die was worn; the hair detail was simply the icing on the cake, not the priime cause of ghosting.
I think you're probably right about the war ending the recessed ear experiment.