The default behavior of WPML is to show WooCommerce reviews in the currently active language only. For example, imagine that your site has two languages:
- Language A
- Language B
If your website is viewed in Language B, WPML will automatically filter reviews and show reviews only in Language B.
You can read more information about this feature on WPML support forums. Most of the topics on the forums will be about showing comments in all languages. This is because WordPress is much more popular than WooCommerce. However, WooCommerce reviews are based on the standard WordPress comments, so topics about viewing all comments also apply to reviews.
Here is a topic from the WPML support forum about this issue: https://wpml.org/forums/topic/show-comments-in-all-languages-for-each-translated-page/.