Thanks for your comment Bernard. The industry accepted definition of private equity encompasses venture capital funds as well as other types of strategies such as buyouts and mezz finance. By natural, the equity of VC companies are privately held thus making them private equity.
Secondly, it is industry accepted that Vision Fund is a venture capital fund as the portfolio companies are, largely, relatively young companies from emerging fields/new tech. We can also infer this through a process of elimination as Vision Fund in most cases does not participate in the secondary market, engage in buyouts of mature companies or provide mezz debt financing.
I've also included links below to crunchbase who classify Vision Fund as a venture capital fund and a link to wikipedia explaining the various types of private equity which includes venture capital.
I would be keen to know your thoughts on why its not a VC fund and am happy to defend my point.