According to the law, citizens can dispose of their personal property by will, and they can designate one or more legal heirs to inherit their personal property.
The Inheritance Law clearly stipulates that a self-written will should have three formal requirements, that is, it should be written, signed and marked by the testator. Therefore, your grandfather's will should be signed and marked with year, month and day.
A will can be notarized, but it doesn't have to be notarized. If there are several conflicting wills, the last will shall prevail. If there is a notarized will among several wills, then the notarized will is the most effective.
If there is no other will, no notarized will, and this will is not illegal, then this will is still valid without notarization and witness. Unless other heirs can provide evidence to overturn the will, it will have legal effect. The statement of the relevant departments has no legal basis.