When upgrading from Forma LMS 3.0.17 to 3.0.22, it doesn't seems that the XML language was applied during the Upgrade phase, as when I entered on Language Mgmt, it was still showing the older strings instead of the newer ones. I'm not sure if it's the intended behavior, but it also may also means that updating/creating new strings to the XML file it will not be reflected on user installation.

The facto it seems to be the default behavior because it could override custom strings user replaced on their translations, but I believe it should import the missing strings from the XML core files, but I don't think it's happening.