No, they are not.

I am pretty sure they don't believe in abolishing all forms of government excepting national defence and contract enforcement.

What they actually want is for the government to support their priorities. Like preserving open space and parks and zoning against development, environmental regulation, support of infrastructure and transportation improvements, education and science research etc. But they don't like paying taxes much, they aren't interested in the government regulating their reproductive choices or recreational drug habits, etc.

Those positions are far from libertarianism. The accurate political term to describe this general world view is "elitism".

Silicon Valley types as described above are just pro-business types that fetishize technology and are socially liberal. Or what used to be coastal Republicans before that party was overrun. Libertarians they certainly are not.

In the same way, there are people who correctly call themselves 'democrats' that don't believe in the kind of gun control that is part of the official party dialog.