Come Learn Blueprint Multiplayer with me! (aka 's a Glutton for Punishment)

I hope you don’t mind me hijacking the thread, but I guess my issue might be quite informative.

Alright, so in my setup the player character blueprint is using the controller rotation yaw to set the rotation of the character mesh. Upon keypress, the “Use Controller Rotation Yaw” option is set to false, meaning the camera rotates freely around the character, without the mesh rotating along. This is kind of vital for the gameplay, so it basically should only be executed when having authority. The usual approach would be the following:

And the notify function:

This is NOT working. All clients as well as the server see the mesh rotating while it should not. Only when playing as the server the mesh stops rotating, and only for the server of course.

After fiddling around a little, I came up with the following solution:

Now my problem is that I don’t understand why it works and if it has become vulnerable for hacks.

Edit: I might also want to stress that this is the only working solution I have found.