In earlier versions of the game (OFP, Arma, Arma II), calling "setFlagOwner player" would cause the flag to appear visually on the back of the player model.
This no longer happens in Arma 3.
Simple repro mission attached (setflagownerbug.stratis.zip) . Preview the mission in the editor and switch to 3rd person. After 10 seconds "theFlag setflagowner player" is called. You can see the flag come down the pole.
Expected - the flag should then appear on the player's back.
Actual - the flag disappears completely.