Yes, I recall Dean giving some very limited info on this issue, back in the day. As far as I recall the answer was along the lines that Chernarus map basic coordinates are somehow set, and you have to build the whole new map from scratch to make it bigger.
However it just created more questions, and left many things unanswered.
Is this whole claim (that current Chernarus+ is non-expandable) still valid, considering the Enfusion engine transition? Has anything changed?
Also is it possible to build, say, map twice or 4 times the size of the current Chernarus if you start from scratch?