The terminology ‘Class A’, as Mitch has stated, is used primarily in the automotive industry to describe a particular type of surface - continuity matched Bezier (aka single span) surfaces. Rhino can, of course, create these surfaces but matching and analysing them is more than a little difficult - and sometimes not possible. The VSR tools are the first step in Rhino getting these features and the capability of creating explicit surfaces like Alias.
T-Splines does not create Class A surfaces; when you convert a TS mesh to NURBS the result is a multi span Degree 3 surface.
In practice, you might use T-Splines to rough out some concepts and then VSR tools to produce some initial surfaces.
‘Class A’ is often mis-defined and derided by some as marketing bullshit, but if you want to work beyond concepts in the automotive industry then it’s a reality.