It does mostly presume that you have things in common with your friends. At least it's not everything they read, only what they repost. Also, if something was reposted from 8 hops away by someone you don't know, you still see the OP's handle and can follow it.
The only value this brings is that it's much easier to hit "repost" on things you like than it is to go send links to everyone. People do this already, it's just awkward, and friends get annoyed from chat notification spam.
The question is what percentage of my friends have more than 50% of my interests? I read plenty of interesting stuff on HN that isn't interesting to a lot of my non-programmer friends. So I post it in the "software-dev" channel of my dev friends' Discord. I don't post it in the server I share with the folks I play video games with, or my friends I cook food with.
Channels of info are only as valuable as the signal/noise ratio is. That's the whole point of RSS in some ways. You follow a lot of specific curated news sources that may be low-volume but high relevancy. "All the stuff my friends enjoy enough to repost" is likely below 50% relevant to me, just because I have a lot of friends who do a lot of stuff that I don't also care about, or don't care about that much.
I kinda doubt my friends read enough good stuff to have 50% of their stuff be more than 1-2 things per day, which is pretty bad volume. What percentage of what you read would you re-share in an average day? You also have to remember that some of that overlap of stuff is stuff you also probably got from the same place they did. If my friend and I both read HN, me resharing something from the homepage of HN has a low chance of being something they haven't already seen too.
My opinion is mostly based on the number of slack and discord channels in servers with my friends that I have to have muted because they have plenty of chatter about articles I don't care about. Filtering by topic is much more valuable than filtering by which human shared it most of the time.
The only value this brings is that it's much easier to hit "repost" on things you like than it is to go send links to everyone. People do this already, it's just awkward, and friends get annoyed from chat notification spam.