Hi David,
Welcome to the grey area of SEO, according to the rules of Google you're not allowed to mark up your reviews with the proper schemas when you don't show the complete reviews about your company or service. So as long as you don't show them you can tell Google whatever kind of reviews you have since nobody is going to make sure that's really the case. So indeed Google's just accepting the reviews on faced value. They're automatically approving them since about 1,5 years and if you ask me it didn't increase the quality of the results.
In this case they marked up the text with the rich snippet data for reviews, more info could be found here. There's not much you can do about this, you could try and file a spam request but that's really a long shot.
Hope this helps!