To address one minor detail: the extra points you get for completing a game are not taken into account when calculating the ratings. All the ratings are calculated with your actual BayesELO rating and the points for completing a game are added afterwards on Fizzer's side. Given the matchups people are receiving at the top end of the ladder (or at least the matchup cases i've seen), I'd say it's very likely that these extra points are also not considered when giving people new matchups.
i just had a discussion on discord and wanted to know, if your rating is affected and how much it is affected, if you got an opponent who's playing some games until he loses one and then surrender his other games and leaves the seasonal ladder.
This has no definite answer. Since the player gets his initial matchups assigned randomly (i think), they can be against anyone. If he got matched against what is going to be the top 5 of the season and he beats them all, then leaves after losing to someone, he will have an extremely high rating. If he wins against the bottom 5 of the season and then loses a game, he'll have a way lower rating. Since his rating is what influences yours, the more significant rating he had, the more significant impact it's going to have on you.
I always thought it would have a significant effect on my rating. Then i heard a long time ago, that it shouldn't be the case or if, than just to a very minor extend, that you can almost ignore it.
So what's the truth?
So in conclusion, both are the truth, given specific cases.