[MC-276636] Modified client can do high-damage mace attack instantly from the ground

A modified client can send (valid) movement packets, faking a 10 block fall in just a single tick, not taking any fall damage, while doing a strong mace attack "mid flight". See the attached videos with an unenchanted mace in survival mode, reproduced on a vanilla server.

Example modified client code:

    private void maceAttack() {
        LocalPlayer player = minecraft.player;
        Vec3 pos = player.position();
        ClientPacketListener connection = minecraft.getConnection();
        connection.send(new ServerboundMovePlayerPacket.Pos(pos.x, pos.y + 10, pos.z, true));
        connection.send(new ServerboundMovePlayerPacket.Pos(pos.x, pos.y + 0.3, pos.z, false));
        minecraft.gameMode.attack(player, hitResult.getEntity());
        connection.send(new ServerboundMovePlayerPacket.Pos(pos.x, pos.y, pos.z, true));
    }