Canon’s extra lens ring that it introduced to most of its new RF mount glass has proven popular. Many people set it to control aperture, which is a traditional place to set aperture going back to the days when manual aperture rings were the only option. Sony is now rumored to be putting such a ring on its new refresh of the GM series of lenses, starting with the 70-200mm f/2.8 GM OSS II.
The customizable ring on the Canon RF system was one of the main three selling points for the new mount, when the EOS R was first introduced. The additional pins on the mount were to allow additional electronic communication between lens and camera. The old mount had only 7 copper contacts. Sony’s E mount was originally patented with 8 contacts but was released from the get-go with 10 pins, which likely means it has the bandwidth to support the feature.