Piastri gifted Norris victory in the Sao Paulo GP Sprint on Saturday morning in Interlagos.
The Australian qualified on pole and led the race from his McLaren team-mate before adhering to team orders in the latter stages.
With Norris winning, and a post-race penalty relegating Max Verstappen from third to fourth, he reduced his deficit to the Dutchman by three points.
Speaking after the Sprint, Piastri revealed that it was always the intention to swap places when the opportunity arose.
As it was, the pair managed to complete the move seconds before the Virtual Safety Car was deployed.
“We spoke about it before the race and when we were going to swap,” Piastri confirmed.
“The gap never really got big enough to do it at a convenient time, but that was always the plan at some stage.
“I think we pulled it off as well as we could.
“We got a bit close with Max under the VSC, but still the most points for the team, which is, of course, what we wanted.”
As the Virtual Safety Car ended, as Piastri entered Turn 4 on the final lap, Verstappen was locked on to his gearbox.
Illegally so, officials later ruled and penalised him five seconds.
For much of the 24-lap encounter, the top four ran in close proximity, with Piastri heading Norris, Charles Leclerc, and Verstappen.
The Ferrari driver finally fell victim to championship leader on Lap 18, who then chased down Norris.
However, he was never really in a position to challenge the Brit, who strategically enjoyed DRS from Piastri before the Aussie moved aside.
“It’s not as fun as winning,” the Melburnian said of finishing second to Norris courtesy of team orders.
“But, I know the position that we’re in. We’ve been talking about this for months now and, you know, this is really the first time that we’ve had to enforce it.
“Yes, I would have preferred to have won. But, again, it’s a Sprint.
“It’s the same points for the team and being realistic, I don’t have much to fight for in the drivers’ standings.
“We knew this is something that could and probably would happen at some point. But I was fine with it.”
The 23-year-old went on to note that he was willing to help Norris again should the situation call for it.
“We’ve spoken for months now about working together and doing what’s right for the team,” he admitted.
“That includes both of us as drivers in the team.
“We’ve probably spent months planning a million scenarios now, but until you actually get into the race and see what you have, it’s very tough to do.
“But I think we’ve showed multiple times in both directions that we’ll help each other out when we need to.”
For his part, Norris was thankful if somewhat sheepish for the help of his team-mate.
“I think it’s one of our strengths is we work very well as a team,” he began.
“I don’t think there’s probably any other team on the grid that work as well. So I’m proud about all of that.
“We’re fighting for a constructors’ and we’re fighting for a drivers’, and we want to help the whole team achieve both of these goals.
“Obviously, from a driver’s point of view, it puts us in a slightly different position.
“I’m not proud to win a race like I did today,” he added.
“It’s not how I want to [win.] I’m not proud of it, basically.
“So, you know, I’ll work hard to go and do a better job in quali later and put myself in a better position for the race.
“We want to avoid [team orers] as much as we can but at the same time, we sign up for this.
“We have to work together as a team. We get told what to do. We have a boss. We do the best we can to help each other out.”