Wait, tell me more about this? I've never heard of it but this sounds much more similar to what is practiced by eastern christians. Where there is also a 40 day fast before christmas, then the twelve day feast ending with epiphany/theophany. And in those branches lent itself is preceded by a 3-week period of increasingly strict fast. So in some years depending on when easter lands you can start fasting again very shortly after christmas ends but is still understood as a completely separate thing.
I don't know anything about the rhineland one but I could see how this could eventually mutate into one super long fast with a break for christmas, but also maybe isn't seen that way by the people doing it.
