What’s your description of Metaphysics? To answer your last question first since you're right, in my thinking, that is always implied. If any human (necessarily meaning humans with that seemingly unique human Consciousness) pursuit including expressions are necessarily Fictional, then so is This expression, and so on. But the so called liar's paradox, paradoxically affirms my hypothesis (and paradoxically, I have to assume my hypothesis is valid for this present point to work). It reveals a defect that (yes, I am necessarily also that defect, always implied) one would think doesn't belong in Truth. Paradoxes reveal a crack in the foundation...therefore of Fiction. Truth (if we are even qualified to address It, and, we're not) wouldn't have any cracks.
As for your reference earlier to my suggestion about Language. Sorry, I don't doubt you were clear, I rather lack the confidence to be sure in my reading: are you suggesting Language and, I would presume, Reason, pre-exist their emergence in the human experience? In Kantian (and I think Platonic, see the slave and the triangle, anamnesis ) terms, are you suggesting Reason and Language are Real (even, have a higher place in the hierarchy of Reality than human perception, for e.g.) and that, even if you were to concede that all of our experiences are Fictional, Language and Reason were already there to build that, otherwise, how did we get to our seemingly pure ideas? If that's what you're suggesting, pardon my simplistic terms, this is what I think, to keep it simple. Before Language developed into the very structure of human Consciousness, it existed as images stored in memory and used by the organically aware human animal to organically trigger conditioned responses helpful to survival and prosperity. A roar means run, no need to "think" about it. Language and reason developed out of that X means Y (note X isnt really Y). And there's no room for any explanation of that process of evolution here. But that process is Real. However, the idea that Language, and especially sophisticated reason, pre-exist our Fictional Structure in which they were both incubated and reached their current form, I think is a falsehood we are compelled to believe in order to support that fictional structure. Anyway, that's me making assumptions about your point, and trying to express mine briefly. I hope I haven't frustrated you by missing yours entirely.