In https://www.mediawiki.org/wiki/Topic:Xfksbqg9mj2azs8n a user who is a member of acl*Project-Admins but not a member of Trusted-Contributors wanted to create a new project by using https://phabricator.wikimedia.org/project/edit/form/4/

Per https://phabricator.wikimedia.org/transactions/editengine/projects.project/defaults/4/ we hide the Editable By field which is set to Trusted-Contributors due to past vandalism.

This triggered the error message “You can not select this edit policy, because you would no longer be able to edit the object” although the user had no option to see or select the edit policy.

This is confusing.
We may want to adjust the error message via an override in https://gerrit.wikimedia.org/r/plugins/gitiles/operations/puppet/+/refs/heads/production/modules/phabricator/data/fixed_settings.yaml .
Note that this error message still needs to be generic as the same issue in theory could also happen with other groups/configurations that do not involve Trusted-Contributors.