The author states: "The heuristics are necessarily imprecise because TLS extensions can change anything about a connection after the ClientHello and some addit

The author states: "The heuristics are necessarily imprecise because TLS extensions can change anything about a connection after the ClientHello and some additions to TLS have memorably broken them, leading to confused proxies cutting enterprises off from the internet." Can someone elaborate on a specific instance of this where a TLS extension lead to breakage? I don't doubt the author, quite the opposite - I'm interested in reading more about the specifics of it.