Porsche have said in many interviews the coating is for cosmetics rather than performance.
Like most electric cars, when driving “normally” you don’t really ever touch the brakes as the energy regen that kicks in when you step off the accelerator pedal slows the car down so effectively. Porsche were worried the discs would develop unsightly surface corrosion from lack of use for some drivers - the coating keeps them looking good.
Primarily for cosmetics since it generates much less brake dust, but it's also has a shorter stopping distance due to increased coefficient of friction from increased contact area and seems to be more resistant to fade.
The Taycan freewheels when you take your foot off the accelerator and only regenerates when you hit the brakes. This is quite different than most other electric cars.
That's just a default configuration difference. You can configure it to do lift-off regen if you like. There's also a camera based auto-regen mode that can switch between coasting and regen based on the distance to the car in front.
Philosophically, Porsche believes it's easier to drive a car fast when one pedal is solely responsible for accelerating and one for braking. Having the throttle be responsible for acceleration and light braking makes it difficult to modulate speed consistently. You can even see the philosophy at work on their gasoline cars, in Sport+ mode the anti-lag system pretty much removes engine braking.
