Which looks similar to Charles Proxy too... https://www.charlesproxy.com

Or Burp Suite. It's hard to design a brand new UI for the same functionality...

I think it's just an example of "convergent evolution". A tool like this will necessarily have a list of requests and a way to easily examine each one of them in detail. One of the well-known Windows equivalents is not that different either:

https://www.telerik.com/fiddler/web-debugging

Yes, I, Creator of Proxyman here, admit that I'm heavily inspired from Proxie UI too from the beginning day of Proxyman. Thank you for the first pioneer, who is dedicated to ship the Debugging tool on macOS app

Which in turn looks suspiciously similar to every browsers request inspector.