Draw it slightly simplified and add a label in red and inside a red circle called "C". This is the new lower power feed point and you can now ignore the old node in black called "C": -

[![enter image description here][1]][1]

Can you see that R3 is in series with RW2 and equally, R4 is in series with RW1 and hence the balance is maintained.

RW3 is a red-herring because it doesn't imbalance anything when its value changes; it just affects the "gain" of the circuit.

  [1]: https://i.sstatic.net/ULCrk.png