[SPOILERS] Why does the WOL have an extra Spirit Vessel?

[Iscah]

All six of them are "spare" now, really. I think G'raha has one (he loans it to us in Azys Lla when we're trying to free Tiamat) but we don't know what happened to most of the others. They're effectively keys for accessing Allagan systems, so they still have value to carry around.

If you've done the Void quests following on from the Shadowbringers role quests, we use one of the vessels (supplied by Urianger) to transport Unukalhai's soul to the First, so perhaps we kept that one.