as mentioned, if it doesn’t have turn signals you need one.
the law was probably made forever ago before turn signals were standard… i assume it was like a bike where you had to stick you arm out the window and make signals to tell other drivers what you were going to do.
so purpose of the sticker is to tell drivers to look on the other side of the car for the hand gestures… but since the car has turn signals and brake lights it’s stupid.
basically, the HTA needs a do-over, there are too many obsolete and grey area laws.