After a month of ads with Google Ads Shopping campaigns and continuously identifying, day after day, a significant discrepancy of clicks on Google Ads and Sessions in Google Analytics (as well as another analytics tool that brings numbers very close to analytics's numbers), I contacted Google Support. For more than 3 weeks, after numerous interactions and different/contradictory suggestions/explanations/solutions, it finally seems that my case has taken a direction towards the solution, but the result that has been passed to me, despite having convinced me that it is the which may actually be the cause of the problem, was not satisfactory to me. I was really disappointed with the procedure Google Support provided me, and would like more explanations and information from the community.
What I got last through Google's support was this:
"There are two methods for logging out of a session: a session can be opened on the same day or on several days, weeks or months. Expiration by time: After 30 minutes of inactivity At midnight Campaign Change: If a user enters through a campaign, he leaves and then comes back through another campaign. Why is there a discrepancy between clicks and sessions? I have separated this link from the help center that explains specifically what we said in connection If you've noticed one of the following discrepancies between clicks and sessions, use the troubleshooter for clicks × sessions to identify and resolve issues. As well as reporting the discrepancy between clicks and sessions up to 20% is considerable. "
Among the Google help links passed by the support, it has not been clear to me whether a 20% less discrepancy in the number of sessions in relation to clicks is normal or if only when the session number is higher (the phrase "A single user can open multiple sessions" suggests that it is only normal when the number of sessions is higher).
But if it's really normal that the number of sessions is 20% less than the number of clicks, I'm led to think of the possibilities:
1 - Analytics fails as a tool to count 100% the number of sessions (accessed by the same person or by different people). Once when a click occurs, the user is taken to the site and must count as a session. If it is normal for analytics to compute 20% fewer sessions than clicks, soon the analytics fail to compute all the sessions.
2 - Google uses this explanation to be able to charge up to 20% more clicks than clicks that actually occurred from its users.
I do not like to believe in either hypothesis, first to rely on Google Analytics as a tool to identify sessions and because their numbers are very similar to that of a third analysis tool used (built by my ecommerce platform), and also for not believing that a company like Google would lend itself to deliberately charging 20% more clicks from its customers. So I turn to the community so maybe someone will bring me a third alternative that I have not been able to identify and/or a totally different explanation from the one I received from the support (as they have done so many times over the course of those weeks).