I'm pretty sure this is incorrect. SV has been host to tech companies (for the varying definitions of "tech") throughout the decades, from early processor and PC companies, video game companies, early internet companies, and Web 2.0 companies.
Do you mean SF or SV? Silicon Valley traditionally ended at Palo Alto in the North. It was only recently, ie. last 10 years, where tech companies moved out from Palo Alto. Only a few scant companies were outside of prime Silicon Valley until then.