That would have to be a pretty selective report, carefully obscuring how staggeringly stupid the thing that McNair did was. His suggestion had little chance of working unless he was correct that casting the Killing Curse was Voldemort's plan anyway, in which case it was redundant at best, and in fact risky even then (since authoritarian bosses prefer ideas to come from them, not subordinates). I have trouble imaginining how he imagined that conversation would go. "That hadn't occurred to me, Mr. Sallow, but an excellent suggestion, thank you"?