Hi D and welcome,
When SU 7.1 came out, the cad import was already taken out of the free version and substituted with a temporary solution; a plugin that Google said would not be supported in future releases.
So yes, you can put it that way; it is a catch for "professionals" to purchase the pro version - while hobbyists will probably not need this feature too much.
There is now another plugin being developed by a forum member here:
http://forums.sketchucation.com/viewtopic.php?t=31186
Hope it can do what you'd like to import.