I will add that people with severe Alzheimer's disease, who have lost almost all of their biographical memory and with cognitive abilities that have fallen to depressing levels, retain complex motor skills.
In addition, different types of memory are not only localized in different areas, but also encoded in different ways. Henry Moulison, a man who had his hippocampus removed at age 25, lost the ability to remember anything for more than a couple of minutes, but retained the ability to acquire fairly complex motor skills. He was taught some difficult tasks, which he later solved with great ease. He was surprised at his skill, as did not remember how he was taught this.
Mechanical memory is not directly related to the information that we receive during life.
The same as disconnecting an external drive from a computer, the data from the drive will no longer be available, but the device itself will continue to function.
Moreover, amnesia is not a loss of memory - it blocks some data (short-term or long-term), in some cases people may forget what happened in the coming days, but the rest is fine to remember. Sometimes selective amnesia occurs, in which a person cannot remember something, but again remembers a lot.
Moreover, even at the time when amnesia has just begun, due to mechanical memory, people can go home , to work or to places where they have often been - even if they do not remember the address.
Since the blocks of the brain are distributed in such a way that everyone is responsible for their own processes - amnesia can also be in different blocks, a similar disease contributes to the shutdown of some mechanical capabilities.
It all depends on what caused the amnesia, and which brain block is affected. As far as I know, it is the phenomenon of amnesia that does not destroy it does not disrupt the work of the brain (destroying cells and connections) - so that this phenomenon is always temporary.
But if there is a direct destruction of the connections of the cerebral cortex, neural connections, cells etc. in the event of injury, hemorrhage, stroke, lack of oxygen and other factors - a serious violation of the processes for which the damaged brain block is responsible - in this case, recovery may not occur.