I agree with that, most groups should en will be open. I suppose this is an edge case where a closed group is needed. This might change in the future if the plugin advances for example. For now it would be usefull to prevent clutter in the public dutch community and the prevent people from participating if they dont import the BAG. Atleast for now, this strict helps to keep the quality of the import high.
Note that in the public forum we have a sticky post where users can request local bag imports. And ofcourse, if non importers have questions about the bag, they can ask there.