I Counterfactual quantum computation on interferometer

[artis]

I watched a video on the topic by Sabine Hossenfelder.
Now it is said by many that this proves the photon "knows" something in advance because a certain state of a certain beam splitter can be probed in theory without the photon ever encountering that beam splitter because it took another path. The reason it took another path is also exactly because of the state of that beam splitter that it "probed" without actually probing it.

Now maybe I have got this wrong but what is so exotic in all of this?
Isn't this analogous to for example a loop of pipe with a pump and two parallel valves with different diameters.
If the water flows in such loop and I randomly close either of the valves the water then simply takes the route through the other open valve but given their different diameter I can know which path the water took by simply measuring the pressure before the valve.
So in this loop the "detector" would be a pressure sensor while in the quantum example the detector is a light detector and water is a laser beam and valves are beam splitters.

Now you might say that my valves are different diameter and that gives it away, but in the quantum example I think that translates into the angles and positions of the beam splitters , because only certain beam paths create constructive interference and therefore hit the detector.
So why is this then considered something "mystical" ?

 

[Demystifier]

Interesting analogy with pipes.

The reason why is this considered "mystical" is because some people try to explain what's going on by thinking only in terms of a classical particle, without taking into account the wave function.

See also Elitzur-Vaidman bomb: https://en.wikipedia.org/wiki/Elitzur–Vaidman_bomb_tester