@thomasfuchs by "conjectures with no evidence" do you mean philosophy? 😀
I feel like it's a "bite the bullet" consequence of the philosophical position of materialism: mind & conscious experience are a function of macroscopic physical bodies (mostly our brains) and as such in principle can be modeled by computation.
Of course, the computation needed for a full brain model is infeasible, obtaining the full starting conditions for a particular human's living brain is physically improbable, and if anyone uses this line of thinking to claim that LLMs might be conscious, they're making an unjustified leap or trying to sell something.