The default behavior of WPML is to show WooCommerce reviews in the currently active language only. For example, imagine that a website has two languages:
- Language A
- Language B
If the website is viewed in Language B, WPML will automatically filter reviews and show reviews only in Language B.
This WPML feature is often discussed on their support forums. Most of the topics on the forums are 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 link to one of the topics from the WPML support forum about this issue: https://wpml.org/forums/topic/show-comments-in-all-languages-for-each-translated-page/. If you would like WPML to show comments (and reviews) in all languages, please try implementing code snippets suggested on their forums.