Facebook "does" this and I put "does" in quotation marks because even when I change the newsfeed sort order to "Most Recent" I still see posts I've already seen

Facebook "does" this and I put "does" in quotation marks because even when I change the newsfeed sort order to "Most Recent" I still see posts I've already seen from hours ago jumbled in with things happening more recently, and if I leave the page and come back, or merely hit the refresh button I'm back to "Most Popular". Combine that with the ever annoying problem of leaving the page, suddenly seeing something interesting, hitting the back button and being presented with an entirely different order of sorting news items forcing me to go digging through my friend's timeline on their actual page .... I guess what I'm saying is I don't trust them to not fuck up two streams on Instagram the same way they've done it on FB: to the point of being completely useless as a dichotomy.