This sounds more like a spin-off of the old investment adage: "Buy stock in the products you actually use." If you spin that argument slightly as a proxy purchase, it makes sense that VCs would be investing in the products that their other startups are using heavily.
As an super-small-time investor who only owns stock in companies whose products that I use and enjoy, I can't knock them for it. For me, the logic is that whenever I tire of using something or no longer find it valuable, presumably I'll have early insight to sell the stock before the rest of the world catches on. I don't know if that same logic applies to proxy buying, but I suppose if you're intimate enough with your companies to know if they're abandoning Github for something else, as I don't know if pulling venture capital is as easy as selling the stock.
As an super-small-time investor who only owns stock in companies whose products that I use and enjoy, I can't knock them for it. For me, the logic is that whenever I tire of using something or no longer find it valuable, presumably I'll have early insight to sell the stock before the rest of the world catches on. I don't know if that same logic applies to proxy buying, but I suppose if you're intimate enough with your companies to know if they're abandoning Github for something else, as I don't know if pulling venture capital is as easy as selling the stock.