Plugins GLPI-PROJECT » Generic Object

In an itemtype, User is part of the fields to be entered.
When creating, modifying an item, I can enter anybody from the GLPI users' list as a User for this item.
But when I search by User, is/is not, I have only user 'glpi' available in the proposed list.
A restriction on users' list seems to apply in the search option.

Same of massive action (Modify, User).