It is inline with Google policies as long as you add the rating to your organisation & not to an individual product.
If you check the different guidelines
(sources: https://developers.google.com/structured-data/policies & https://developers.google.com/structured-data/rich-snippets/reviews)
- When you have multiple entity types on a page, we recommend you mark up all entities on that page to help Google algorithms better understand and index your content
=> OK -both organisation & product are being tagged - Make sure the review or ratings markup refers clearly to a specific product or service as shown in the examples above
=> OK - aggregate reviews are done on item: organisation - Review and rating markup should be used to provide review and/or rating information about a specific item, not about a category or a list of items.
=> same as above - Make sure the reviews and ratings you mark up are readily available to users from the marked-up page. It should be immediately obvious to users that the page has review or ratings content.
=> I imagine you put the rating quite visible on the page, you probably also provide a link to the original source (trustpilot)
Don't see any issue here.
rgds,
Dirk