The Illustrated TLS 1.3 Connection: Every Byte Explained
"Because middleboxes have been created and widely deployed that do not allow protocol versions that they do not recognize, the TLS 1.3 session must be disguised as a TLS 1.2 session."And, from the bottom of my network-protocol-guy's heart, I hate them and everyone who's ever even seen one with the fiery passion of a million very angry suns.