I looked into this once (lol a couple weeks ago). Its supposed to enable "live" pages, so that on the new tab, new threads are added without having to manually refresh the page. I dont think its working though.
It would end up with behavior like the lemmy bug that had new posts just show up and take over your page. Not sure its something we even want if im right.
That being said, i could be wrong on the above. @ernest would know.