grabbing brakes

Yes the definitive reason is the hydraulic brakes are not used much as most braking is done by regen assist.
So the rotors get very rusty from lack of brake pad contact and make all kinds of noise and makes them extremely grabby in the rain.

Easy fix is to get up to speed say 50 mpg's and put the gear shift in neutral which turns off regen and you are then only using pure brake pad and apply the brakes firmly a few times. This scrubs the rust somewhat off the rotor. You will then notice how poor the regular brakes are without regen. Then put the car back in drive. Make sure you do this when no one is behind you. Get familiar with putting the car in neutral, its a good thing to know in any car.

Some rotors are to far gone and pitted. Bend over and look through the front wheel slots and see how rusty they are.
Both before and after the procedure I just listed.

 

Mine does that because you don't use the friction brakes that much. When your rolling put the car in in neutral and step on the brakes. That over rides the regen brakes and mocks the rust off the rotors.

 

I thought I just said that.