One discrepancy root cause we've seen before is the scenario where Branch will classify an install as a reinstall or open. We remember the history of a particular user via their IDFA or Google Advertising ID (in addition to using a few other methods) and will detect whether the user is actually a new user or a returning user who had previously uninstalled your app. Facebook has a different mechanism that is limited to 180 days. Branch in some cases has detected reinstalls that occurred more than a year later.
Updated about 3 years ago