Why is the Solar separate instance from Waking Sands / Rising Stone?

[Sove92]

So after a few months or so SE redesigned it in a patch so that the Solar was changed to become a seperate instanced room from the rest of the Waking Sands that only the player themself could enter, and this has continued with the move to the Rising Stones (and the Intercessory in Camp Dragonhead - Haucherfaunt's so-called 'Falling Snows') also being instanced too.

The Solar has always been behind a locked door. SE always knew the zone is going to be crowded so they put the door in there to act as a camera barrier so players on the other side are not rendered.

SE never put in a patch note that says when they stopped sending other player data in these zones, but it was somewhere between 2.1 and 2.2, because you could still see other players during the early days of Rising Stones (which is why it's designed the same way).