Yes, it's an assumption. An assumption the team that ought to have won would have knealt out the clock, which they could have done. Maybe they'd have done something crazy and turned the ball over, but really, they'd have knealt out the clock. It's a 100% lock.
The comment you're trying to make about recency bias isn't clear. But then, I also can't imagine how it could be relevant, either.
This game was won by the Saints, and a terrible blown call gifted a possession to the Rams instead. End of story. If you're ok with factors like that influencing who's in the championship game, by all means, watch with baited breath. I have no interest in the outcome.