Grand Slams are independant of the WTA and don't follow their guidelines
and they simply use this to "fix" draws in favour of their home players if aseed withdraws.
Basically there is no rule.... they use whatever they like
If Jen was seeded 5th she would have been moved to #4 spot.
Roland Garros did this in 2001 when Lindsay withdrew, they moved Mauresmo and Tauziat to more "favorable" spots in draw and both lost in 1st rd.