I've never heard that one. Kunos goes back a little farther than GT5. Netkar Pro was in 2006 so maybe GT4?
I couldn't find the article in which is shows their inspiration but this was what popped up:
"
Marco Massarutto's idea for
Assetto Corsa stemmed from a lifelong passion for motorsports and racing video games. He and co-founder Stefano Casillo were particularly influenced by the realism and depth of classic sim racing titles, which inspired them to create their own highly authentic simulation.
Specifically, Massarutto has cited two games as being instrumental in his decision to enter the sim racing business:
- Grand Prix II (1996) by MicroProse, which he described as a "game changer" that addicted him to real-world Formula 1 and motorsport.
- Grand Prix Legends (1998) by Sierra Sports, which impressed him with its deep simulation, car feeling, and the fashion of F1's golden era, making him want to be involved in the industry.
This passion led Massarutto and Casillo to start KUNOS Simulazioni at the end of 2004, with the goal of creating a job related to their love for the genre and focusing on realistic car handling and physics. The studio developed
Assetto Corsa at an R&D office located just inside the Vallelunga international racing circuit, allowing them to collaborate closely with real racing drivers and teams to achieve authenticity. "