For theories specific to the BU story, see the BTS Universe WMG page.
The most obvious connection is with Jin, where the dove who was previously dead revives - with the video then cutting to Jungkook running; however, there's a second main moment with Hoseok. Hoseok's only individual scene before the bridge appears after Jungkook loses consciousness - it cuts to Hoseok among tree stumps, with Jungkook (seemingly as a corpse) lying in the same position as in the previous scene in the background. It's likely Jungkook's dreaming, but that this isn't a normal dream, but a vision showing him where Hoseok currently is - after all, Jungkook disappears in later shots, implying this is indeed reality.
Therefore, his use of the shell before the dance break functions as a magic call towards the other members. This could also imply that the other members also had the same power or other powers of their own.