All I get out of the "sport touring" designation is either a sportbike with bags (Ducati) or a regular touring bike with sport plastic and a more aggressive riding position (ST100).
I am completely clueless on how sport touring is different from touring. For me, adventure touring has to include at least a few thousand miles of dirt.
Every once in a while a pure touring rider will show up at an MSTA event and complain that the route is too twisty and challenging to be fun for them to ride.