In both the web and android clients, probably iOS as well, the weekly average intensity minutes is wrong for new garmin connect users. It is averaging in the weeks in the past year before the account was created and therefore much lower than the actual average weekly intensity minutes.
Web version of the report here: https://connect.garmin.com/modern/report/51/wellness/last_year
Weeks without data should be excluded at the very least prior to account creation, it's a paint to wait a year for it to catch up.