How do they not leave each other feedback on upwork?

Question

Upwork

Here's a fresh piece of work. Start - October 2017. End - too. Some money is made there, almost $1k. The work is not mine.

How did they complete the work so that no one left a review for anyone? I have seen this many times already.
It used to be 3 years ago. And now it's not.

Answer 1

If the review is bad, then toprated can remove it.

Answer 2

How can Upwork prevent a customer from leaving a review? This September, I closed the old fixed price contract due to the lack of activity (but payments went through in the past). I left a review (5 stars) and after two weeks it became visible on the project page and in the customer profile. And I have 'No feedback given'. As far as I remember, I wasn't required to leave a review either.