I never said S & C fudged their numbers. I said they don't conform to any known standards. Instead of saying accepting the manufacturer's word, I should have said accepting the manufacturer's test methods and rating definitions.
I'm going from memory here, but when I applied S & C Mk V circuit switchers at 69 and 138 kV, I recall several different application categories numbered A, B, C, etc. The IC ratings varied between categories. We used the Mk V for transformer protection/switching, and I recall it only had about an 8 kAIC rating for that application.
I guess the difference between S & C and manufacturers of ANSI rated gear is that ANSI is an independent body that publishes standards detailing the minimum construction features and test procedures, and defines the ratings. The manufacturer may try to fudge, but you can ask for certified test results and compare them against the ANSI standards.
S & C (for circuit switchers, anyway) doesn't follow standards set by an independent body. S & C finds a niche for products that don't fit the ANSI world, thus giving them a proprietary product that is difficult to specify for competitive bidding and more often than not leading to sole sourcing. It's a brilliant marketing strategy to eliminate the competition. If the customer doesn't require the assurance of ANSI, then buy S & C. In my experience, the S & C circuit switchers are only marginally cheaper than an ABB ANSI-rated live-tank breaker (HFD or LTB).
Having said all that, I have used S & C products several times in the past (usually fuse gear) and agree with Mark that they have a good reputation.