That's interesting. The detection part like "Am I in a SBWorldPortal, if yes, teleport me" is server side, I am pretty sure of that because on the SDK the code involved request the GameServer object. But it does not avoid the possibility to have something clientside too. I don't remember if on the beta we had these tooltips so  may be it's not on the current version we are working on (or maybe it is but we still have to found it!).
 
Edit: Btw I have the confirmation that "Claustroport" means "Teleport inside current map" and "Teleport" means "Teleport to another worldmap".
See SBGame.Content_API the functions ClaustroportPawn and TeleportPawn.
Edit²: The tooltips are actually SBGamePlay.TooltipActor and some have the tag "InteractiveLevelElement...