When settling an estate, I understand that the notary does not have to certify ownership of a property if it is sold within 10 months of the death. Is this true?

No. The purpose of the real estate certificate of ownership, published at the land registry office, is to record the transfer of ownership following a death. However, article 29, last paragraph, of decree no. 55-22 of January 4, 1955, states that it is possible not to issue such a certificate if, and only if, all the real estate is divided up within 10 months of the death. In this case, you are not proceeding with a division but with a sale.