This point system is similar to the MMR system. It comes from the concept that more skilled opponents are worth more points, and less skilled is worth less. So if you have a match of a champion player against a novice, if the champion wins, they don't get a lot of points. However, if the novice wins, they earn a lot more points. There's a lot of variations on this type of system and it's present in many multiplayer games in one fashion or another.
You can consider it the evolution of the Hephaestus League. In that system, teams earned points for wins, regardless of who it was against. You could beat 10 novices or 10 veterans and it's still the same points. We want a system that gives value to the teams and also acts as a balancing factor.
So along with more skilled teams earning more points (the more you win, the more skilled you show yourself to be) we balance it by pairing the skilled and less skilled. This, ideally, will lead to some balanced matches which are more enjoyable to play and watch.
It's kind of like what Veteran Matches and/or GoIO MMR should be in the right conditions.
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Timers come into play from experience. I've seen tournaments that lasted way too long because a match or two went over an hour each (Sniping is just the most common). There have been events where the lobby wasn't timed and matches took an incredible amount of time to start. Today we had 6 matches on each stream. With 3 minutes each, that's 24 minutes of just sitting in the lobby. Then there's the added time of creating the lobby and getting the majority of players into the lobby. More than a few matches went over the 3 minutes before starting. So it's likely to be over 30 minutes of not being in a match.
If we move it up to six minutes, you could be looking at over an hour of that. 3+ hours of GoIO ever weekend for 9 more weeks would be stressful on a lot of people.
That being said, we can increase the lobby time (not to mention the other ways of getting more lobby time). However, I can't justify increasing the match time regardless of how loose it makes you.
For subs, they can play on your team as long as they want. However, they can't play for a different team immediately. I have adjusted the wording in the rule to make this more clear. If you have a sub for Team A, they can keep playing for Team A. If they want to play for Team B, they have to wait 3 weeks. I hope this makes sense.