This is the number of elements of medium sized space truss roof, nothing special...
By the other hand, when working in a computational Design context like in Grasshopper, those number of elements shouldn´t be treated as abnormal, in my opinion.
But even without leaving Archicad, the number of elements that potentially Archicad needs to manage with the new curtain-wall tool could easily be much higher than 16.000 elements...
I have the impression that the present GH Connection plugin performance is because some kind of "performance bug", so to say. But this is Just a supposition...