According to Google, this update only applied to product reviews written in English. It took six days to finish; ending on September 26.
The Google algorithm improvements are now completed. However, the new rollout has been the subject of some critisim within the SEO community.
This was discussed by Barry Schwartz on Search Engine Roundtable in What We’re Seeing From The Google Product Reviews Update.
High-quality product reviews are intended to be rewarded by these algorithm changes. According to Google, it will prioritize these product reviews in the order of search results.
In other words, if you were impacted, you probably need to work harder on enhancing the information in your product reviews. Discover a way to differentiate it from the competitors by making it special.