I’m not sure it really affects the result. Wind speeds on Saturn top out at around 1,000 miles per hour. Using some back of the napkin math, the rotation “speed” at the equator should be well over 20,000 miles per hour. Is that not enough to get an accurate assessment?
Perhaps accurate but certainly not precise.
You think 5% error is "accurate"?
For psychology studies, sure. Not for landing airplanes, unless they're paper ones. Depends on your context, I guess.
I guess the only rotational property you can be sure it has is angular momentum. Various parts of the gas can rotate in different speeds and ways that even change over time.