I join as "Helgisa" -> Helgisa will be the name in stats.
Then I join as "NextLvLPlayerOrSomething" -> NextLvLPlayerOrSomething will be the name in stats, and Helgisa is now gone.
Then I join as "Helgisa" again -> Helgisa will be the name in stats, and NextLvLPlayerOrSomething is gone.
Stats will always follow on name changes (aslong as you don't get a new ID(game license/ code)
Edit: to answer your latest post, Yes