Surgeons see a lot of cases but it seems they're often a bit quick to say "wow that's really unusual" or "you have a particularly severe case". DC is much more variable than the textbooks say.

I have DC progression in a number of locations on both hands, including both index fingers and thumbs. On the right had the progression of the index finger and thumb has been minimal for years, no functional problem there. The left hand is worse - although surgery corrected the index finger some years ago, the base of the left thumb is slowly contracting. Not yet to the point of requiring correction.