Brandon seems adamant that we understand that Vax is only heavily suggested to be a place.
Also Khriss' words are:
"Nothing is known of Vax, its peoples, or any Shards that may or may not be located there. All that is certain is that it has a manifestation of Investiture in which people are Initiated differently than on Sel, Scadrial, Nalthis, or Taldain."
All we know is that Vax has a manifestation of investiture that people can possibly be initiated in, but contrasted with the methods on known shardworlds, not compared.
In your WOB referencing 6th of the Dusk and shards having to focus their awareness on things to "move" there because location is irrelevant and they have infinite access but finite awareness limited to what they focus on, then "location" in the Spiritual Realm is more akin to "awareness".