I'm probably missing something here: author says that the split diff doesn't work for him, but doesn't say why. His ideal diff is pretty much the same as a split-diff but with redundant context removed (context is only on the left, not on both left and right). What utility does he get out of removing redundant context on the RHS of the pane?
In my understanding the author wants to flip the diff around: instead of looking at changes themselves, the author wants to look at code and see if there are any associated changes.
The article is light on detail, but my guess would be that author wants to look at code and browse to implementation/callsite to check if appropriate changes are there.