I think you're assuming people just went straight to rank 6 cloak and then are using additional runs to get mementos. No one ever said they did that in the thread.
What's happening is during the upgrading of rank 2-6 some people are taking the chance on some of those runs to do the 2 middle areas (or 1 middle area like I did), this allows you gain more mementos and go further in the tree while also still upgrading your cloak to the max that's possible this week.
Hence why it's risky, but payoff is big.