I could not find that claim in the article, but perhaps you are referring to an earlier version of the article that the author then updated? The performance problem with TCP is that it imposes a strict ordering of the data. The order in which clients receive data is the same as the order in which servers send data. So if some packet fail to reach the client, the packet has to be retransmitted before subsequent packets can be sent (notwithstanding the relatively few non-ACKed packets that are allowed to be in flight). I think this problem is what the author is referring to. And that it would be nigh impossible to get all network equipment that sits between a client and a server to a more latency-friendly version of TCP.