https://github.com/phaserjs/phaser/blob/master/src/gameobjects/group/Group.js

"Sets the angle of each group member."

It doesnt "Set" the angle, it adds a value to the angle of each member.

This method isnt called "setAngle", so its kind of makes sense, but the description just doesnt match what the method does. Also, there is no "setAngle" method then.