The line is an agreement to a pre-determined outcome quid pro quo. If I agree to give your team something (no goals against) if you give me something (also no goals against), this is quid pro quo and match fixing.
Playing for a tie happens all the time but, without a quid pro quo agreement, it still requires a lot of effort and aggressive defense. You either cede possession in non-dangerous areas and have only a couple players transition in counters, or you hold possession and high press to win the ball back.. In a 60-90 minute game, if a game is fixed at the team level, you are going to notice if all the strikers decline to shoot at open nets or if defenders refuse to make hard tackles in dangerous areas. Game-throwing by one or two individuals is harder to detect (they usually get subbed out).
The question is whether the tournaments or leagues have rules against match fixing or, if they do, will they make examples of the teams. Surf Cup apparently let such teams advance to finals.
https://fut411.com/post/surf-cup-scandal-update
It is also a fair question whether clubs have their own ethical rules in this area.
Anecdotally, I will point out that I once saw two FRAM teams, an 07 and 08 end up in a position where they played each other in group play. If the 07 team beat the 08 team, it would have advanced to the final. Both teams had the same coach. That coach sat down during the match, didn't say a word and let the two teams play their hearts out. The 08 team won and neither team advanced to the finals. That coach was Nunez and he forever has my respect for that.