MultiDirectory tries to write in subdirectories all document fields (dirty or not)

I need to configure multiDirectory for users. This directory contains 2 sources.
One SQL directory and one LDAP directory.
I only want to be able to write to SQL and not to LDAP so I set the widgets as view only (see ldap-ui-contrib.xml).
The problem is that the MultiDirectory creates a new document for each schema of the subdirectories and passes the new document to each session to update the entry.
When the document is created, it has all fields dirty by default so the LDAPSession is trying to update all fields, even if they were not dirty on the original user object. So we get an error from LDAP because we are trying to write to it.

Please find attached the contributions that should reproduce this.