I will always report surrenders as "Assisting Enemy Team" and this is why
This post assumes a 5v5 game
Anything can happen in a game. Just to start here is a list:
- People can throw
- Your team can get really weird catches and make a come back
- A baron steal can turn a game around
- Minions might hold off the other team long enough for you to respawn
- Minions might backdoor
- That player you've been yelling at all game might step up and be really good
- You might be able to hold out for 20 minutes and farm up and push to victory
- Their jungler might try to solo Baron and die making it a 4v5
- Your end game might be stronger then theirs is and you can win at 50 minutes
- Someone can DC from their team
OR
- Your team surrenders at 20 and there is no hope for any of that
Any of those things can happen at any time, and that is a small list of all the things that can change a game. When your team surrenders there is no larger form of letting the other team win.