Less then 1% of Facebook's value is VC funding.
That's not how it works. LPs create a portfolio mix across asset classes and each LP has generally different mixes based on their risk profile. If you're an LP and can't get into a Sequioa/Benchmark/etc fund but still want to diversify asset classes into VC then a "2x fund" might still be attractive to be able to diversify into. There's so much to unwind here, but long story - it's not that simple at all. I agree with the OP's assertion about Matt Levine's view.
Example: https://twitter.com/ZacharyDeWitt/status/1112554272929910785
Edit: Another point worth noting - hedge funds as an asset class are notoriously not outpacing index funds (and in many cases actually losing value), yet they still get funded: https://www.nytimes.com/2018/07/12/business/hedge-funds.html