@mattotcha As a member of a few dementia caregiving communities I've heard a number of stories where the loved one with dementia shows some lucidity shortly before death. Not necessarily pre-dementia behavior but more lucidity than shown for some time.
It is normal during the disease for people with dementia to have good days. These are probably from the brain creating new neural pathways that restore some function. But since dementia is progressive these improvements are often soon lost.