Electron flow due to impedance?
The analogy is badly flawed in several ways, one of which is that water does not really "congest" (let alone that it does so more in a wider pipe, or that a narrower one represents lower impedance).

In a low impedance device, electron flow is less constricted. This makes the device difficult to drive, and in particular to develop a voltage across it.

If you push against air, it has less impedance than water. This is why you can move through water by moving your arms, but not through air (even if you simulate the support of floating by standing on a skateboard).  Likewise, a ship propeller could hardly work on an airplane.

If you want to develop pressure in a pipe, you will have the best luck if the other end of the pipe is closed, or has only a pinhole leak (this is like a very high impedance, analogous to an insulated gate on a field-effect transistor). The next best thing would be a pipe which is open, but long and narrow. The complete opposite is wide-diameter pipe which requires you to produce a huge flow of water in order to develop significant backpressure.

In other words, when we are propagating electronic signals represented by a voltage, the "congestion" is desirable. It is easier escape of electrons (lower impedance) which makes the loading harder.  Voltage is transmitted with the greatest ease when impedance is as high as possible (if we overlook issues like stray capacitances and certain kinds of noise).

If we want to transmit power, then impedance matching becomes important: not too low an impedance and not too high and impedance: just right. The fluid analogy is that it's next to impossible to paddle a canoe in thin air, but also very hard to paddle one through a pond of molasses. The in-between impedance of water is more efficient than either.

Fluid analogies don't really apply all that well to voltage signal propagation in small-signal electronics because fluid pipe networks are used for moving fluid, rather than keeping fluid flow small while transmitting information via pressure. The analogies require students to imagine unusual ways of using pipes, which is a bit of a failure, since analogies should be comparisons to something familiar.