I know some Vj 72s are modified to run at 21600 bph, the Rolex 727 being a prime example, but I suspect we'd have heard more about it if anyone had got one running as fast as an el Primero! The components weren't designed to run twice as fast as "normal" speed so the amount of revision required would have resulted in a new movement really.

And how would that scale work, without a separate hand to run off? The chronograph seconds hand will take 60 seconds to rotate once round the dial, so that makes the additional scale pointless and redundant from what I can see. So it looks to me as if it's just an addition for "style" as you surmise, in which case I find it a bit misguided, as that garish orange scale detracts from what would otherwise be quite a handsome dial (though better if the registers were equally sized and finished the same).

Maybe someone can put me straight, but I just can't see how it would be functional...