Parent directories listing limited to 50 entries

Vocabularies administration in Web UI handles without any issue more than 50 vocabularies.
But when choosing a parent, the listing is limited to 50.
This can be seen in Google Inspector.
For instance, the country directory content is listed with:

http://localhost:8080/nuxeo/api/v1/directory/country?pageSize=0

(see childListing.png)
whereas the continent directory (its parent) is listed with:

http://localhost:8080/nuxeo/api/v1/directory/continent

Double-checking the result shows "pageSize":50 in the response. This means with directories bigger that 50 entries, some entries will be missing in the UI.

Expected result: the parent entries query should include pageSize=0 to allow full entries set retrieval.
Workaround: none since the vocabulary form (nuxeo-xvocabulary-edit-layout) is dynamically called through nuxeo-layout and thus tempering with the nuxeo-resource to pass the page size is not possible.