Easy to check: try to speak with someone talking foreign language you don't know and estimate what percentage of what they said you understood from tone of voice etc. I would guess it's less than 80%.
That's very easy and very wrong. Let's say you have a 100 page book. Page 1 contains fundamental knowledge that allows you to understand the rest of it. If you skip page 1 then you won't understand the other 99.
How much of the book will you understand if you only read page 1?
That then raises the question: what is a unit of communication?
If communication is 20% verbal and 80% nonverbal, and if communication is very nonlinear in understanding (as with your book example), how do we know what 1% of communication is? What does it mean, and how can we tell that the figure is correct, when our main or only way of detecting whether communication succeeded is through understanding or lack thereof?
But tonal information can be parsed without lexical understanding and vice versa.
Somebody cursing in French can still be interpreted as anger even if you don't understand French, and written profanity can still be interpreted as anger even if you didn't hear it spoken.
Tone and language do complent each other, but neither is a prerequisite for the other like your book analogy would suggest.
> but tonal information can be parsed without lexical understanding
Parsed perhaps, but it's so context sensitive that it's not useful, save for extremities. The same tone of voice can have so many meanings based on what's actually being said and yet another if you add context.
