Can you confirm that there are no duplicate product reviews in WooCommerce?
Please try deleting the imported reviews in Site Reviews (and empty the trash!). Once you have done that, try importing them again using the “Import Product Reviews” tool.
So this is how the Import Product Reviews tool works:
Site Reviews searches the comments table in your database for reviews (WooCommerce saves reviews as comments).
Any WooCommerce reviews that do not have the imported meta_key are imported into Site Reviews.
Once a review has been imported, Site Reviews adds the imported meta_key to the WooCommerce review to prevent it from being imported again. This is what prevents duplicate reviews.
Keep in mind that Site Reviews will only import the original WooCommerce reviews, but it will not import replies to those reviews.
The review count in WooCommerce includes the review replies.
The reason Site Reviews does not import review replies is because comments can have multi-threaded replies whereas reviews in Site Reviews can only have a single reply. Also, anyone can reply to a comment (i.e. WooCommerce review), so there is no way to ensure that your reply to a review is being imported and not someone else’s (in cases where a review has multiple replies).
If you would like to redo the import to ensure that you have imported absolutely all of your WooCommerce reviews (minus the replies), then this is how to do it:
Delete all of the reviews that you previously imported into Site Reviews and then empty the trash.
Activate the code snippet (it will run immediately after activation) and then deactivate it. The code snippet will delete all of the imported meta_keys from your commentmeta database table, allowing Site Reviews to import them again.
Run the Import Product Reviews tool.
If you followed the steps above correctly, all of your WooCommerce reviews should be imported into Site Reviews.
If the number of imported reviews does not match the number of reviews in WooCommerce, it’s likely because some of those WooCommerce “reviews” were actually replies.