I’ve seen some swirl because the siphon jet hole on some are smaller in diameter, especially in some of the late 1990’s ones. Some have a larger diameter siphon jet hole, and they tend to not swirl much. This particular toilet was either made in Mexico or Thailand.
Kingstons that swirl the entire bowl have "Water Guard" appended to the name. That said, I have seen some overpowered Kingstons swirl a small amount around the trapway mouth.
This gen Kingston was invented in 1992 and it was discontinued in 2013 because I went to a mall that was renovated in 2013 and it had 2013 Kohler Kingstons. The next gen Kingston was invented in 2009 and it was discontinued in 2019.
I can see why people don’t like these, I personally don’t find them too bad I feel like it depends on the pressure like the one I filmed it’s actually pretty decent and it even gurgled.