There's no doubt as to the magnitude of Grove's influence, but the assertion might be a little strong.
I'd argue the Traitorous Eight were the first to break the cultural mold and set the tone for modern entrepreneurship in the Valley. Two of the traitorous eight (Bob Noyce and Gordon Moore) later founded Intel, and another (Eugene Kleiner) established one of the Valley's most storied VC firms.
The culture of the Valley is really interesting, Stanford Professor Frederick Terman probably should get the most credit. He influenced companies from the very beginning.
Also Hewlett and Packard are often cited as the two that really set the tone and culture of valley, The HP Way management style was modeled by numerous companies.
Hewlett and Packard were influenced greatly by the Varian brothers whose company in the 40's were some of the first to have radical ideas of profit-sharing, stock-ownership, insurance, and retirement plans for employees.
Fairchild still had the Eastern company mindset of top down driven which with poor management led to the Traitorous Eight but the culture was already started in the Valley.
I'd argue the Traitorous Eight were the first to break the cultural mold and set the tone for modern entrepreneurship in the Valley. Two of the traitorous eight (Bob Noyce and Gordon Moore) later founded Intel, and another (Eugene Kleiner) established one of the Valley's most storied VC firms.