Gerin,
The numbering is denoting two things: the iteration of the structural system, which can then be used in whatever building form. And the iteration of a particular building form design.
The 4.1 structural system has not been uploaded yet, but is basically reduces the amount of wood needed substantially. Although it won't have been full-size tested yet.
The Studio v0.2 download used the 4.0 structural system. Hence the connection.