I have been buying collecting rebuilding Hurst and Muncie shifters for over 25 years and over half of the ones I had
had the rubber on the forward levers or they had a trace of the rubber where it had been.
I have also seen the rubber bushings on unrestored cars
Some didn't have the rubber
I also had a NOS set that had the rubber
I don't know why some didn't have the rubber as the notched hole was designed for the rubber bushing
If they were not going to use the rubber, they would just need a round hole
here is a pic of some extra ones