I think you reach the wrong conclusion.

IMO, Jordan started with Mat and Egwene for pratical reason. Egwene's storyline was by a long shot the most complex and had the most sub-storylines involved. RJ needed to establish fairly precisely the timeline of all events that needed to happen at the WT before he knew how much story-time Rand needed to spend in AD before his meeting with Tuon. Once Jordan had outlined the WT events far enough, he'd knew exactly when the Seanchan attack happened, which determined when Tuon returned to ED, which determined when she met Rand. That provided the timeframe RJ would need to use to organize the events in AD, from Rand's arrival to the Falme meeting.

It's the same for Mat and the Caemlyn events. Some of those were determined by when Egwene reunited the Tower. Then, it's Mat's story and Elayne that were determined the timeline of events between the Seanchan attack and the Fields of Merrilor.

Once Jordan had Mat/Elayne and Egwene figured out (and for Egwene in particular, that required some serious outlining to make sure everything would work and how many story-days that needed to work), he would know when Perrin must deal with the dreamspike and when he must arrive in Caemlyn. Like Rand, that provided RJ with a timeframe on which to organize the rest of the events in Perrin's storyline. It was fairly easy to create gaps or speed a development in those storylines. It wasn't so with Egwene. If RJ needed to stretch or condense there, it affected tons of small developments in sub-storylines.

Brandon didn't say RJ worked a lot on Egwene all the way to the end, by the way. He really gave the impression he mapped out in more details than the others her story up to the Seanchan attack/reunification.

It may well be that from that point it's not at all Egwene's story that would be useful to map out TG. Nearly all the subplots have been resolved, her storyline is fairly streamlined again.