A Query About The Hextech Chest System

If you've seen my recent post you'll know that while I am a very old player, I haven't played the game at all since about 1-2 months after the Hextech Chest System was introduced and they were still working kinks out (like 15 months ago), so I'm sure my queries will have been asked before...

Is it still the case that you need to personally score an S OR be on a premade where an is S scored? If so, for clarification, if you queue with 3, and one of the other 2 scores the S, does that count, or does it have to be a full pre-made 5 to count (which would discourage parts of the reasoning I make below)?

(Assuming that is still the case...) But more to the point, Why? I understand wanting to encourage friending and teams and non-toxic play... but it seems like Riot would be ignoring (best case) or punishing (worst case) Solo queuers, particularly in ranked.
I mean it's pretty tough to luck out in getting a team where everyone agrees and works well enough together... to have one where it enables a person to get an S rank is something that seems relatively special. So why would Riot, effectively, actively discourage players from going into Ranked Solo, and maybe making new friends, by rewarding players who already have friends & group up?

It strikes me as... disappointing. Discouraging even, if everything weren't new-again to me and I didn't have that renewed innocence of "I can have fun and encourage my team to be the best it can be" attitude. I was just in a game where, while there were minor play style issues between Bottom and Support in the early game, once Laning ended, our team was on top for the rest of the game, and worked together as a team, enabling everyone else to do very well. To the point that the Jungle and Top Lane went S and S+ (Mid was probably pretty close too).

It seems to me, rewarding an evenly matched team that could pull that off would serve to increase Morale and encourage beneficial Team behaviours. So it comes back to, Why is this not the case? Did they answer these questions somewhere else? Regardless, whatever their reasons, they feel wrong, personally... but I may be in the minority.
/shrug Not going to stop me from trying to enable my team to win, though.