That is, it assumes that there is a difference between "effects of consciousness" and "consciousness itself" -- in the same way that a connection is implied between "hearing" and "sound".

Not quite. What I'm saying is there might be a difference between the computation of a thing and the thing itself. It's basically an argument against the inevitability of Tegmark IV.

A Turing machine can certainly compute everything there is to know about lifting rocks and their effects -- but it still can't lift a rock. Likewise a Turing machine could perhaps compute everything there was to know about consciousness and its effects -- but perhaps it still couldn't actually produce one.

Or at least I've not been convinced that it's a logical impossibility for it to be otherwise; nor that I should consider it my preferred possibility that consciousness is solely computation, nothing else.

Wouldn't the same reasoning mean that all physical processes have to be solely computation? So it's not just "a Turing machine can produce consciousness", but "a Turing machine can produce a new physical universe", and therefore "Yeah, Turing Machines can lift real rocks, though it's real rocks in a subordinate real universe, not in ours".