How to check if player is in air?

Don't know if it's properly but maybe worth mentioning. I see that in the lua file movement controller of Jack in Lumberyard's stater game:

    local thisTm = TransformBus.Event.GetWorldTM(sm.UserData.entityId);
local diff = math.abs(utilities.GetDistanceMovedDown(self.prevTm, thisTm));
if (diff < 0.001) then
self.NotReallyFalling = self.NotReallyFalling + 1;
end
self.prevTm = thisTm;

or here

    -- If we're not moving up or down then we're not falling.
local zDiff = pos.z - self.landedBecauseSupportedPrevTm:GetTranslation().z;
if (math.abs(zDiff) >= 0.1) then
isFalling = true;
end

So I guessed the idea is just store the previous position then check the height between previous & current position to know if it is falling or not, but I tried commenting out these code, and see that Jack still fall & land properly, so maybe it not how it works to determine if Jack is in air, maybe I guessed wrong.

The code I see that determine if in air is slope angle

    function movementcontroller:ShouldLand()
local angle, realAngle, dist = utilities.GetSlopeAngle(self);
if (realAngle < self.Properties.Falling.SlopeAngle) then
if (dist <= self.Properties.Jumping.LandingHeight) then
return true;
end

Is this a hack? I feel like this is a hack, I think Physic module should be responsible for checking if player is in air/falling.

I see that there is property m_bFlying in class CLivingEntity. Does anyone know how to get this property? Or Is this property still usable?