Hi Pils,
the reverse action is pretty much not changed or scripted by us - it is default X-Plane behavior.
I agree that it would be more realistic to require the user to have the levers at idle first before being able to engage reverse thrust, but I also have to concede that the movement is much more natural in the real aircraft - you can´t really attempt to pull up the reverse levers with the throttle NOT at idle, the force pulling them up and back will automatically move your thrust levers to the aftmost position.
In addition (although this is not a prime concern of me, as my stance is always realism > user experience), we would get a million bug reports "OMG, reverse is broken, WTF!!!!!!!" if we implemented this ;-)
But yeah, you are technically correct!
Cheers, Jan