I see your "flat plane of silicon" and raise you "a mush of tissue, water, fat, and blood". The substrate being a "mere" dumb soul-less material doesn't say much.
And the idea is that what matters is the processing - not the material it happens on, or the particular way it is.
Air molecules hitting a wall and coming back to us at various intervals are also "vastly different" to a " matrix multiplication routine on a flat plane of silicon".
But a matrix multiplication can nonetheless replicate the air-molecules-hitting-wall audio effect of reverbation on 0s and 1s representing the audio. We can even hook the result to a movable membrane controlled by electricity (what pros call "a speaker") to hear it.
The inability to see that the point of the comparison is that an algorithmic modelling of a physical (or biological, same thing) process can still replicate, even if much simpler, some of its qualities in a different domain (0s and 1s in silicon and electric signals vs some material molecules interacting) is therefore annoying.
"Annoying" does not mean "false".
Aside from a priori bias, this assumption of absurdity is based on what else exactly?
Biological systems can't be modelled (even if in a simplified way or slightly different architecture) "with silicon arrangements", because?
If your answer is "scale", that's fine, but you already conceded to no absurdity at all, just a degree of current scale/capacity.
If your answer is something else, pray tell, what would that be?