My theory for why the trust does not act as a perpendicularity is becuase it is purely the physical representation of Ati/Ruin. We know that shards tend to warp the three realms around themselves a little bit, but the Atium itself might not have enough of a cognitive or spiritual presence to pierce through the three realms and create a perpendicularity.
Or do you think that any large amount of investiture located in a single area should create a travel point and that something else is being done to prevent that? I'm not sure, but I think It's possible that the substance of Atium exists mostly on just one realm.