This is a great idea! I think that it works well for hand knob.
For robotic applications, it would not work well unless you overspec the driving motor. The overall moment of the armature and some of the magnetic effects would make it tough to use.
Addition. If you read the article you'll understand.
For the "heavy knob" the author built, you can also use the flywheel found
in old radios, or in cassette recorders.
j7
Some years ago I built a similar circuit and made my experiences with it.
This kind of incremental sensor was only usful for armature application. It worked not so fine when the rotation was very slow.
When someone uses stepper motors with 4-coils a snap-in effect can be made by contact the not used coils together.
Make a simple short circuit to the not used coils.
An advantage is:
The output voltage of the used 2 coils increases (because of acceleration during snap-in effect) and the slow rotation sensitivity is much better.