Join Date: Apr 2019
Location: Middle OH, USA, Earth
The little blue sign is telling you it is ready to do parking assist if you want to park the car. The READY light just means it is at a stop and it is ready to be driven.
One should put it in Neutral if going through such a car wash. The owners manual says to that automatic car washes "are not recommended."
Yes, it does have a feature to prevent roll-back, although I have to engage with the brake pedal on some slopes.
My experience, high regen, and one-foot driving style:
Coming to a level stop has no problem engaging the brake.
Coming to a stop light with a slight nose-high slope will engage the brake after a little roll-back.
Coming to a stop light with a steeper nose-high slope requires human foot assistance to engage the hill holding brake action.
Coming to a stop light with any nose-down slope will not engage the brake and human foot assistance is required until ready to proceed.
These features are covered in the owner's manual/iGuide. I suggest reading it and loading the iGuide onto a smart phone. iGuide has a decent search function to find this information.