Ben:
I think your title explains it all.
A brand new course has no consensus on where it ought to rank, unlike the older ones. There is a huge rush to judgment when the course opens, but it’s 100% based on first impressions, which partly explains why new courses come in hot and most fall down the list in the years that follow.
There is also a consensus about who are the great architects of all time and therefore (indirectly) how many places they deserve out of 100. But for anyone still active, the consensus is unclear because we still have more to do. The first test for Childress Hall will be how it compares to Tara Iti, Ballyneal, and Rock Creek. The panelists are trying hard to arrive at a consensus of where it fits on my own totem pole first, and they are influenced by each other’s opinions. I don’t know what my glass ceiling is, but I must be close enough to wear a helmet.
By contrast, new architects don’t have that ceiling yet, so it’s easier to make room for their first really excellent course - by definition, it adds to the variety of the list.