My exclusion list in the latest release of avast is identical to yours and I use Normal level.
Why? You mean why did they change the default exclusion list?
I guess most of us allow the avast team to make that decision, they add and change other elements of the avast interface as they find necessary for the changing environments in which we all work. I think we would need to defer to the team (who are rather busy I understand trying to finalize avast 5) to intervene and explain the changes in detail. No doubt they may change again with avast 5 and yet again with Windows 7.
It could be a lot of explaining … but with what value?