This can only be used for tablets that are not display nor system
integrated (eg. intuos models). The mapping of tablets with a builtin
display remain in g-s-d/GsdDeviceMapper.
This is a vast oversimplification of GsdWacomDevice. This one
has code that is largely unnecessary here (mostly devised for g-s-d),
plus it will be even eventually removed from g-s-d (the functionality
is moving into compositor domain), so the code sharing argument
remains pretty weak.
So, CcWacomDevice is thought to take over, just offering the basic
API we after all need in the gnome-control-center side.