The FX routing is actually really simple – just imagine where the cables are going from and to…
It’s no more magic than cables, you just have to follow where things are plugged in. There is a limited number of sources, and a very limited number of return destinations.
It’s not hard to make a digital feedback loop that your check would miss (FX2 feeds FX1 – your check won’t stop you lifting the FX2 return into FX1) and so at best it’s the TSA of the routing world (security theatre).