Currently if you have a Wait Until specific date followed by an email and you repeat this several times, when someone joins the journey late they are still getting all the prior emails. Per support this is by design which makes no sense. They indicate that they skip all the other wait tiles but not the actions in between those wait tiles which completely defeats the purpose. The only solution currently provided to have someone entering a journey not receive prior emails is adding a custom field to the contact record and setting it via power automate for journey entered time and then create branches comparing that date. This is a poor workaround as contacts can be a part of many different journeys.