It's turned on by default, Fist.Actually it's a switch to enable the fff layer. You don't ever have to turn it on.
And if it was intended mainly for powerful bass ostinati and such, that's particularly strange as most of those fff bass notes sound more like a harpsichord-on-steroïds instead of a roaring grand piano.
But again: below fff, CinePiano can be very seductive.
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Chris, you're right, there is no half-pedaling.