Unable to login using MongoDB + users from Studio

Given a Studio project that defines Users:

Fresh Nuxeo 9.10-HF02 server + JSF + WebUI + MongoDB = login ok

Fresh Nuxeo 9.10-HF02 server + JSF + WebUI + MongoDB + Studio project = login fails

The problem appears to be caused by the fact that, with the Studio project, the user fields have a schema prefix ("user:") while without a Studio project there is no prefix (thus the user lookup fails when logging in: https://github.com/nuxeo/nuxeo/blob/8ae49461f2e99a17d8361fe6972cf5d541c7065a/nuxeo-services/nuxeo-platform-directory/nuxeo-platform-directory-mongodb/src/main/java/org/nuxeo/directory/mongodb/MongoDBSession.java#L360)

I am sure this used to work ok so I fully admit this may be a Studio bug.