If it's the video I'm thinking of they ran a huge number of tests, introduced packet loss and saw some issues. There's a few challenges here… WebPageTest uses

If it's the video I'm thinking of they ran a huge number of tests, introduced packet loss and saw some issues. There's a few challenges here… WebPageTest uses DummyNet to simulate packet loss and in a HTTP/1.x scenario the not all TCP connections in the test will experience packet loss, whereas all the HTTP/2 ones will. Now in the real world if there's packet loss on route how likey is it that TCP connections experience packet loss? Our H2 implementations are still young, this Cloudflare work is one example, until they made this patch nginx didn't support HPACK and there are other issues in other browsers and servers too. As the implementations mature and we understand how to make the most of H2 then performance gains will appear - there's already evidence from people like the FT that there are gains to be made now.