I have not done a comprehensive study of these areas. There may be other information available. The study was criticized on a number of aspects, starting with how reliable were the sexual practice stories of the subjects in the study. How this all relates, is about whether there are things in saliva that kill the virus, and whether there are enough viral particles in saliva, to alter transmission risk. A life without any kissing and an exchange of saliva may be more harmful to a human being than the small risk of transmission via kissing.
Oral sex seems to cause some slight risk of transmission of the virus.
The amount of risk is not numerically quantifiable yet.