The review widget on the product pages displays the reviews specific to that product only, the review carousel on the other hand displays the same reviews across your shop and these reviews could be product reviews or shop reviews.
You can even choose the reviews that are displayed on the carousel from here
And you can move reviews from one product to another or make a product review a shop review from here
To move all the reviews from one product to another, you can do so here https://judge.me/products
You can reach out to us at firstname.lastname@example.org if you have any further questions.
It's possible to change from shop review to product review because in the widget are displayed only product reviews and in the carosel all reviews.