Bungie will tell you that it's because it has "intrinsic" stun capability, even though it doesn't. The real reason is that they juryrigged Chill Clip's coding onto it to make it work how they wanted and Chill Clip bugs out with Radiant/Anti-Barrier. While a Radiant Chill Clip weapon will stop the healing and ability spam of an Overload, it doesn't technically stun them so they can still fire back though it will still destroy the shield of a Barrier Champion while Radiant. Rather than fix this, Bungie just pretends everything with Chill Clip has "intrinsic" dual-stun capability and they went in to specifically block Anti-Barrier from working on Wicked Implement.