Why does "path live_set view selected_scene" not require a live.observer?

I have a patch where a "path live_set view selected_scene" message is plugged into a live.path object. However, I noticed that every time I click a new scene, it sends out the new scene number with no further setup needed. This is great but it has me wondering — why is this being automatically observed while other parameters need a live.observer object to update? What's different about this particular path? Thank you.