I think what you’re saying supports the view that language is structured and actively used—which excludes pheromones. But I don’t see how you get to the next step, of characterizing unspoken acts as carrying linguistic meaning. That is, sign language and not answering a call aren’t obviously in the same category, precisely because not answering a call fails to communicate any particular concept, and because people don’t use various modes of non-answering to communicate various things.