Junio C Hamano [off-list ref] writes:
I am not you, so I can only speculate, but the real reason _could_
be that it makes it simpler to formulate steps 2 and 3 mechanically.
This is somewhat true, however...
I think that approach would make more work to get to the final
state, though.
I found that if I were to add the backpointer, it would have been better
to add it early and avoid this extra work that you mention here :)