Yes, although I suppose the original idea I had for my comment rather got away from me, the reason I brought up TLS 1.3 is that this whole "Guess what KEX [Key Exchange e.g. X25519] to use" feature is only in TLS 1.3, previous protocols always eat a whole round trip to ask "Hi - do you speak TLS and if so what flavours?" and get a reply "I speak TLS 1.2 and I can do this KEX and that KEX and..."

The insight in TLS 1.3 was that we can guess a KEX and if we're correct we win a free roundtrip overhead†. So the history is that in TLS 1.2 you will always eat two round trips to talk HTTPS the first time, though in some cases you can reduce it to only one to "resume" conversations, in TLS 1.3 you can spend only one round trip even the first time if you guess the right KEX, and as few as zero round trips in some specific cases.

† This also means there's a strong incentive to have few KEX options, a new KEX must be unarguably better for a large constituency so that it's worth losing the round trip bonus to get a better KEX until your KEX is so popular that everybody will guess that KEX instead of the previous most popular.