I could be wrong on this as it's been quite a while since I played regularly, but to my knowledge there were 3 states that it read to inform the melee damage: standing still, moving, and mid-air (it didn't have to be a jump, technically).
I do think that even if it didn't operate that way and there were only two states, it was still a better system in theory than the more recent 2HKO systems (so discounting the very inconsistent melee lunge, which plagued Halo 2's CQC). If someone wants to be effective in melee, they're forced to jump and show up on radar, so the efficacy of corner camping was a little diminished - or would have been, if BXR didn't undermine the entire concept (something something added depth something something skill gap something something ????).