While that's true I think that once the feed has been observed in a certain way the advantages of stability outweigh the advantages of showing a tweaked version the second time it is loaded.
if i refresh the page it should be almost the same. maybe a couple new things at the very top, but i should still be able to find the thing i was just looking at.
by comparison, facebook auto-reloads while you're halfway down a page, and wont show you any of the same things. its an incredibly poor experience