It wasn't public knowledge though. At all. It was only known by a select few in some inner circle of altcoin manipulation.
He did a code review for Halcyon under the pretense that he was an unbiased third party. You don't see the problem with that?
Yes it was public knowledge :
https://twitter.com/ATC_SECURE/status/510137631284678656"September 1, 2014
KEY Operating System RC1 - Download at
http://downloads.xc-official.com/atcsecure/KEYOS_PROJECT/Hey guys, it comes with great excitement and a sense of accomplishment that we release the platform on which we will host many of our future services.
In collaboration with Dan Metcalf (ATC_Secure), the core developer of XCurrency, we have created the only non-TAILS operating system environment (based on lubuntu 14.04) that supports full Tor routing. This means all network traffic - not just browser traffic - is routed through the Tor network, ensuring that none of your applications reveal your online identity."