I updated to 6.1.3 and am a bit disappointed to find that Woocommerce structured data for product reviews is still broken in 6.1.3. The issue reported in https://theme.co/apex/forum/t/product-review-error-in-google-structure-data-analyzer-when-using-x6-0-4/27484/7 does not seem to have been addressed at all.
I don’t quite understand why X does not start using the class WC_Structured_Data supplied by Woocommerce for Reviews as it seems you already use it for the Product data (or at least do not override the standard WC functionality).
Still, this would need to be fixed as this prevents reviews from showing up in search and hence has a real impact on SEO/conversion.