Probably true. Though I found quite a few options that are very low: seekins/ vortex at 0.92, Farrell at 0.97, APA at 0.856 or 0.95, and ARCM10 at 0.94. With the 34mm main tube,
I calculate that these rings have only 6.37, 7.64, 4.75/ 7.13, 6.88 mm of clearance (respectively) between the top...