i don't think he can really be Claus though, well if he had never did what he had done, Claus could actually be Claus,
but you have to see it as Claus being his identity, not his soul,
Claus most certainly still exists but has been reduced to what he has left behind (for example his personal belongings or works), both physically and mentally,
the pilot of Claus has long gone, and the Claus you know has gone far away, so that would make Claus a new person, not Claus.