Ok I looked into the 2.2.2 XAR and I find
<backupPack>true</backupPack>
So it is already set to true
I tried to use "Replace history" but it keeps Guest rights...
So i first import the XAR with guest rights in order to have the XWiki.Admin
user!
Then I login as admin and I re-import the XAR again using "replace history"
and then everything is importer as Admin...
Like this, it prevents from logging as superadmin that I don't really like!
Anyway, there might be a light issue around there.
Pascal