Author here. I'd figured they were big, but I had no idea that big until I did a www-wide TLS scan. Here for questions
What I mean here is that TLS up until TLS 1.2 goes like this:
Client: "Hi, I know ciphersuites A, B, C, D, E, F and G"
Server: "OK, let's do C"
And so you can't tell whether the server actually knows A, B, D, E, F, G or even I through Z. They just decided to pick C this time for some reason.
In TLS 1.3 it's sort of better (all of the ciphersuites you shouldn't use don't exist any more) and sort of worse because now it goes:
Client: "Hi, let's do method B, I'll go first, 123456 and a goldfish and the colour yellow"
Server: "Cool, method B works for me, I pick 567890, a swan and mauve"
Probably all TLS 1.3 servers today are willing to do anything method not just method B, since all the methods are shiny and new. But perhaps not, and you can't tell except by failing the connection which takes more round trips.
https://www.shodan.io/report/unklm3m7
Disclaimer: I run Shodan.
You can have a round trip all the time, or just in the case where the client chooses an ciphersuite the server doesn't support. TLS 1.3 makes the typical cases much better without hurting the worst case much.