If you start out making 6 TCP connections then in a perfect network their receive windows all expand in parallel -- 6 times faster than a single HTTP2 connectio

If you start out making 6 TCP connections then in a perfect network their receive windows all expand in parallel -- 6 times faster than a single HTTP2 connection. You're likely to see several HTTP2 connection made as well. There'll at least be a second one in case the first SYN is lost, just like with HTTP 1. The key TCP benefit is keeping a connection open. That can be done with keep-alive as well.