The 200mm f2.0 has the best IS of all lenses. ....
I appreciate your enthusiasm for the 200m, I love mine as well.
When it was released 8 years ago in 2008, it did indeed have the best IS system that Canon had ever put in a lens! It's press releases all claimed 4 stop IS, however I had forgotten that later documentation, ( including right in my owners manual) bumped it up to the 5 stop claim. I feel that the 5 Stop claim was added later when it was found that at the shorter 200mm FL the same IS was able to offer more than it could at higher FL.
It is however an "inbetweener" design, before the MkII IS System was developed, yes more advanced than the IS in the older MkI IS lenses.
Some other lenses with the same "mid-generation" IS system are the 800mm f/5.6L IS and the 70-200mm f/4L IS. They too all claimed 4 stop IS.
These all were a step up from the original 300,400, 500 and 600mm IS lenses, but it was years BEFORE the 2012 release of the MkII 300-600mm lenses which improved again on the system.
Please don't get me wrong I am not knocking the 200mm in ANY way, it is superb! And this being a 200mm thread I'll bow out after this reply on the subject. Nor am I in any way trying to diminish your results as posted which speaks for itself. However, just fyi with the new 100-400mm MkII which also has an improved IS system vs. the 200mm, many of us are getting similar amazing results @ 400mm!