...It was recommended by a friend of my uncle whom neither of us have met. My uncle has been using this site for crypto futures and recently had his account frozen. The site is requesting that he pay a fine in order to release his funds. Is this a scam? ...
Yes, this is a scam. As I understand it, your uncle's friend has stopped being a friend now. Although obviously he was not a friend, as a friend would never recommend such an obvious scam to his friend. You need to learn how to use Google search yourself before investing your money in questionable projects.