No, it's incorrect that signs "point to each other."
There are multiple ways to get to various lines' platforms. This is not signs pointing to each other, this is signs in different places pointing to the same destination.
I live in Tokyo and while I do not go through Shinjuku often as I mostly live and work on the east side, I have no issue using the signs to find the platforms and exits I am looking for.
If you pay attention to what the signs have written on them, they will take you where you are trying to go.
Two signs pointing at each other (I've seen way more of this but here is one example): https://encrypted-tbn0.gstatic.com/images?q=tbn:ANd9GcSe-8IR...
In addition to signs pointing to each other, you also see several signs at once pointing to the same thing in opposite directions: https://skyticket.jp/guide/wp-content/uploads/pixta_46188735...
Or signs pointing the same direction for both East and West exits: https://basyauma.com/wp-content/uploads/2020/01/IMG_5141-2-1...
and https://owl-eat-drink.s3.ap-northeast-1.amazonaws.com/tokyo/...
Same thing at Ikebukuro: https://www.reddit.com/media?url=https%3A%2F%2Fpreview.redd....
There are many, many more examples of this.