Not to sound down on the topic but, that sensor is 5 years old and hasn't really taken off. Filament production has gotten a lot better and it's debatable if a sensor like this is even warranted anymore. There's also the issue of ovality. Filament does not have a circular cross section, so any sensor that looks at it from a single direction is going to be just as inaccurate as the filament itself. On modern filament production lines they have laser micrometers that take samples of the filament from 3 or more angles to get a much better picture of the overall diameter, so they're already producing it at a tighter tolerance than you can measure easily.
But this does come up now and again:
https://forum.duet3d.com/topic/9315/fillament-thickness-sensor
https://forum.duet3d.com/topic/9481/filament-diameter-tolerance-compensation
If it did get supported, and there was a sensor that could accurately measure the filament, I would like to see the results.
