Google Testing Review Count from Sites
Google recognizes that it is not the only review platform, offers a tally of reviews that can be found elsewhere.
Google Testing Review Count from Sites
Google is showing reviews from independent sites in their review total. Unfortunately, this field is not clickable (presumably because it's tallied from multiple domains). It only shows, for example, that X+ reviews on independent sites. Tracking those reviews down would likely be time-consuming, but the user is nonetheless made aware of their presence.