I understand some people saying that the forehead poke was intitially to keep Sasuke away from all the uchiha drama and as protection, but the reason Itachi did that was because he cared about Sasuke which Sasuke learnt later on.
So Sasuke doing it to Sarada and Sakura is just showing that he cares about them too and I suppose is his interpretation of what the forehead poke meant, thus the writer's. I'd say its more of a show for care and love between their family, as Sasuke doesn't poke Naruto on the forehead or anything even though he cares about him. Sasuke doing it is a way to keep his memory of Itachi's care and devotion to him. It's more symbolic than just a kiss or a hug to him.
If you are worried more about itachi's messages not being interpreted correctly by Sasuke then I would say yes they werent. Sasuke randomly decided to try and attack konoha and steal the tailed beasts. But thats the writing for you.