Happens in Western Adoulin as well. There it appears between the warper and the Courier coalition.
I've always wondered what causes Moogles to appear outside of the MH and always in those specific positions :x
Probably just planted there during early planning of the zone. SE probably playing around with the idea of the area being a “Short Spot” or something before deciding to do a full Mog-House would be my guess.
It's just lag causing it. Every zone has the capability to spawn Moogles (probably for oops Moogles, though we haven't seen one of them since ACP release as far as I know), and they sit in that position unspawned when they aren't being used. Something *** up between zoning out of your MH and into the zone outside and it doesn't despawn the Moogle that was in your MH. As soon as you target it your client is told it's not supposed to be there and it poofs. It actually happened in Whitegate all the damn time back in the hayday but the position for unused NPCs/mobs was off the map so nobody ever saw one.