Disgustipated
Deity
It's actually stronger than just the current LOS, you also get a (foggy) map update to everywhere they have explored that you have never seen. I recently became suzerain of a city state on a continent I had barely started exploring the edges of with a boat, and almost the entire continent suddenly appeared on my map.
I was quite surprised that such large areas of the map had been revealed when I was certain I hadn't explored those areas. Like the Australia region on the Earth TSL map. I must say I like this feature as I still feel it takes too long to reveal the map in this game, unrealistically so. Though you could argue it lessons the explore aspect of the game a bit.