Among other things, it is claimed that part of Ferrari's astonishing revival this season is down to the tyre testing it carried out for Pirelli last year.
Over the course of ten tests, the Italian and German teams, and Red Bull, tested the Pirelli compounds to be used this year, albeit using a mule car intended to simulate downforce levels.
On reflection, Toto Wolff admits his team made a mistake.
"It was definitely an advantage for Ferrari that they had Vettel doing it," said the Austrian, "because with his experience, he was a credible test driver.
"If you are driving your car and you are a Pirelli engineer and you have Vettel giving you an input, it is different to Pascal Wehrlein," he admitted.
"The situation was different with us, because Nico and Lewis were in a championship fight, back then, with the current car," he explained. "Both of them said that testing next year's car, with next year's tyres, was something that would at least harm them in their focus of the world championship in 2016. So it was understandable.
"If I could turn back time I would probably push a bit harder for them to drive the new tyres," he admitted, "but we were in a different situation to the Ferrari drivers."