During the 30 years yassoulani experienced that the source didn’t the everkeep and heritage found were one whole however they were in Alexandria’s shard; not the source. So yyasoulani, the everkeep and living memory (the 12th floor of the everkeep) were all in Alexandria’s shard during the 30 year period. In that time the everkeep doesn’t change, only yyasoulani does
So if the WOL defeated zarool ja by being pulled into the dome by taking the first train Sphene couldn’t retreat to living memory because it’s all part of the same shard. The reason zarool ja used the skydeep portal to find Sphene was because before the dome appeared skydeep’s gate was the only thing that connected the source to Alexandria’s shard
So if the WOL took the first train it would have only benefited the WOL/scions as zarool ja wouldn’t have been able to invade and sphene wouldn’t have been able to retreat