You can decide whether the person added to the project should receive an email notification about it. You can simply turn off these notifications by doing the following:
Go to the Team Settings
Click on the "Notifications" subpage
Turn off the "Adding members to Projects", as seen below:
In case you need help or would like to share your ideas with us, please contact the prima:Time Support team by clicking on the black bubble in the bottom right corner of this page 🙌.