The mixin created the method on the frame ie.
function frame:OnEvent(self, event, ...)
-- OnEvent code
end
the xml frames OnEvent <Script> tag tells it to use the frame method.
What I posted replaces the mixin method that gets applied to the frame with your new one ie. it just overrides the old function with the new.
Code:
PVPMatchResults:OnEvent("PVP_MATCH_COMPLETE")
That's directly calling the method applied (copied) to the frame by the mixin (the one that is overwritten by the code in my original reply).
Code:
PVPMatchResults:GetScript("OnEvent")(PVPMatchResults, "PVP_MATCH_COMPLETE")
Call the function currently assigned to the script.