Ok, to me it is obvious because words are themselves symbols - and thus everything that we can describe, and reason about, is symbolic. Us discussing here is symbolic, and a book is a complex, structured, symbolic message. Even if my understanding and your understanding of a particular word may differ somewhat, and there is subjective subsymbolic meaning (e.g. when I read “love”, I tie it with my life experience, and yours is nothing alike), when you compose complex messages those nuances lose importance.

If you read War and Peace, and I read War and Peace, even if our experience of the reading might be slightly different, it will be due to how we react to it, and to which passages we tend more attention; and we will generally agree on what Tolstoy wanted to communicate - not only on the words themselves, but on the world constructed, and the implications of it that are not explicitly described.

Another way to look at it: we don’t have any evidence that we need more than a symbolic approach to replicate what we do with language: and we have built a whole civilization based on written education, which is based in symbols.