Mostly yes. But we do have some processing that bypasses the brain: reflexes for example. The classic example is the kick reflex that doctors test with a small mallet on your knee. Or when you blink as something flies towards your eyes. It happens and your brain gets informed afterwards.
But there are degrees of non-conscious processing, from the heart beating by itself and your guts doing their things, to the breath which will be on autopilot until you take control over it, to entirely voluntary things like moving about your limbs (for healthy individuals).
Maybe the octopuses experience their disconnected brains somewhere on that spectra, where the limbs are semi-autonomous unless it focuses on them? (All we can do is speculate, there is no known way to learn the qualia of being an octupus.)
Thank you for making me breath manually.
https://www.amazon.com/Other-Minds-Octopus-Origins-Conscious...
For an octopus, it must be something similar but with all 8 of their appendages. Some specialize for hunting vs moving, so that’s at least easy to understand, but given they can act independently, I wonder if the octopus feels like the conflict between gut and brain with respect to food.