Not read the article, but isn't the "net result" in the Doppler VOR that the phase difference between the two signals provides the bearing information, without the need for moving parts in either transmitter or receiver
When I was a lad, and learning this stuff, Doppler VORs were new, and some of the older VOR receivers were prone to giving silly results with them. That was in the days when a 360-channel COM set was the height of luxury.
And yes, I confess that I and a certain other person around here took a great delight, years ago, in flying over and trying to photograph every VOR in the area. We gave up at something like 30.
Wonder where those photos are now...