Historical? I know you count many worlds as “understanding”, but I wouldn't until this puzzle is figured out. (Or maybe it's that I like Feynman's (in)famous quote so much I want to keep on using it, even if this means using a narrower meaning for understand.)
I certainly hope that EY means that the problem of the origins of the Born rule is still open, not that the MWI has somehow solved it.
Here's the new thread for posting quotes, with the usual rules: