"The new "Flex Power Mode", exclusively available with the Drive S Mag, is a combination of two software features - Cadence Power Control (CPC) enabling up to 30 percent more support at higher cadences and Progressive Pedal Response (PPR) providing a fast drive response when pressure is applied to the pedals. For a confident handling even in the most advanced trails."
That's a whole lot of marketing speak for a Friday , but basically it's tuning to provide better support at higher cadences and less hysteresis before engagement. The first part of that sounds an awful lot like Shuttle mode:
"Specialized has also introduced something called Shuttle mode. This makes it easier to reach maximum motor power with less required pedalling force, something to help when pedalling at a high cadence when your power output is lower, or for when you're just looking for a fast shuttle to the top of the mountain. In the app, the default setting is zero, but it can be adjusted to suit your preference."