2021 Formula 2 champion Piastri came into McLaren this season following a protracted transfer saga involving Alpine, with the battle between the two teams indicative of how much was expected of the Australian rookie.
Piastri's debut season was starting to be overshadowed by an underperforming car until a comprehensive summer upgrade package gave McLaren's MCL60 a huge boost in competitiveness.
It allowed the established Lando Norris to take two second places in Britain and Hungary, and gave Piastri the chance to clinch a top three in the Belgian Grand Prix sprint race before the summer break.
His Spa result was the latest in a string of strong finishes after a fourth place in Silverstone, where he lost a certain podium due to being undercut during the pitstops, and a fifth place in Budapest.
According to team principal Stella, Piastri's recent run of standout performances are completely in line with what the team had already seen across his debut season, as the 22-year-old now simply has the equipment to turn his form into tangible results.
"I think where he is at the moment is part of the gradient that we saw right from the start at testing and the first races," Stella said.
"I'm not sure [Piastri's progression] has actually accelerated. I think he just took benefit from the car being more competitive, therefore there are more opportunities to show what he is capable of.
"I think this is in line with kind of what we saw at the start. It wasn't easy to get into a McLaren car. We've been here commenting about the characteristics of this car and how much it created issues for drivers and actually feels uncomfortable.
"So, this was apparent already at the start of the season to us, but less apparent outside just because the car wasn't very competitive, so I would say he's consolidating the gradient that we saw at the start."
At Spa's sprint Piastri qualified second and then put in a measured drive in wet conditions, comfortably holding his position behind the dominant Red Bull of runaway championship leader Max Verstappen.
Stella feels that with his mature performance in difficult conditions Piastri gave the impression of a seasoned veteran.
"The interesting point of Oscar is that he's making all this look simple," Stella added. "He's making it look simple that in these conditions you pit, you lead the race, and you go from inters to dry [conditions] and you never kind of make a mistake or so.
"I think this is the most impressive thing that I can witness. And all this is achieved with a pretty unique approach in terms of how calm and considerate he is. And so far, indeed quite impressive."
