My father acted like the way your uncle is and he had a shunt placed in his brain because he had excess spinal fluid. He would talk about things that made no sense and would shuffle his feet. We thought he had alzeihmer disease but it wasn't.
How heart-breaking for the family! Yes, sometimes this procedure does cause adverse changes.
In my opinion, the choice of having the operation and being able to live a better life, & the risks of having stroke, or other complication from the procedure have to be weighed heavily against the choice of doing nothing for the condition.
I have had other significant surgeries, from which I had some memory loss, I attributed this to the anesthetic, and post-op meds.
I had a heart attack and can remember almost word for word every-thing that happened before, during and after the event. So I don't know if there really is a answer as there are no guarantees in any medical procedure.