Why does Neuralink place sensors in the neocortex instead of the old brain?

Question

Imagine a perfect archer whose arrow always hit the target in precisely the area where he wanted it to hit.

Now imagine that each location on the target was an instruction to a human body to make a particular type of movement.

If you wanted to know what instruction was being sent in the signal, what might your strategy be?

One strategy might be to place sensors at every location on the target to determine exactly which area was hit and thus which instruction was being invoked.

Another strategy might be to try to blanket the space between the arrow and the target with sensors and try to predict the trajectory of the arrow.

Intuitively, the former strategy seems more rational, so I don’t understand why Neuralink, whose goal is to build a Brain Machine Interface (BMI) to enable signals to be sent directly from the brain to a computer, seems to be pursuing the latter?

From reading the Jeff Hawkins' book, “A thousand brains: A new theory of Intelligence”, my understanding is that the neocortex cannot generate movement. It has to send signals to the old brain whenever it wants to make any kind of a movement.

So rather than blanketing the neocortex with sensors trying to predict what signal is being sent, why are they not precisely targeting their sensors to the connection points on the old brain which are receiving signals from the neocortex?

My guess is that we just do not have the technology to precisely place the sensors at exactly the locations where they would receive the optimal signal. Is this correct?

Additional context:

For a long time, it was believed that information entered the neocortex via the "sensory regions," went up and down the hierarchy of regions, and finally went down to the "motor region." Cells in the motor region project to neurons in the spinal cord that move the muscles and limbs. We now know this description is misleading. In every region they have examined, scientists have found cells that project to some part of the old brain related to movement.

For example, 1: the visual regions that get input from the eyes send a signal down to the part of the old brain responsible for moving the eyes.

2: Similarly, the auditory regions that get input from the ears project to the part of the old brain that moves the head.

Moving your head changes what you hear, similar to how moving your eyes changes what you see.

The evidence we have indicates that the complex circuitry seen everywhere in the neocortex performs a sensory-motor task. There are no pure motor regions and no pure sensory regions.

“A thousand brains: A new theory of Intelligence”, Chapter 1, Jeff Hawkins

Answer 1

I think I see what you mean now. Why putting sensors in the human region and not in the motor region? The motor generates movements in the body so why don't use this this region to put sensors in and use the gathered information for steering external motors. We can read:

The upper motor neurons in the cerebral cortex reside in several adjacent and highly interconnected areas in the frontal lobe, which together mediate the planning and initiation of complex temporal sequences of voluntary movements. These cortical areas all receive regulatory input from the basal ganglia and cerebellum via relays in the ventrolateral thalamus , as well as inputs from the somatic sensory regions of the parietal lobe. Although the phrase “motor cortex” is sometimes used to refer to these frontal areas collectively, more commonly it is restricted to the primary motor cortex, which is located in the precentral gyrus.

We see how this region is interconnected with sensory input (like the somatic sensory regions). The motor region corresponds with the thought procees also, obviously, therby changing the thought. If a person is disabled the motor processes are disrupted. This can have influence on thought processes obviously but the motor initiating first thoughts are not influenced. So if you connect these thought processes in the neocortex (the motor areas are situated in the old cortex) you get the purest initiator of the external motors.

The big problem is of course how to integrate your sensors outputs with the external motors. To address this takes a lot. Experimentts with non-paralysed people as well as theoretical work.