The "fun fact" here is that TLS version negotiation does not really work. Which is why in TLS 1.3 it still technically is using a TLS 1.2 handshake with an exte

The "fun fact" here is that TLS version negotiation does not really work. Which is why in TLS 1.3 it still technically is using a TLS 1.2 handshake with an extension adding the new version. But appart from that: Having the ability to have a new version is a completely different concept from what people usually call "cryptographic agility". The latter is usually used to describe a system where you can pick and choose from a variety of algorithms, good and bad ones so everyone gets what they want. Which TLS unfortunately still does - TLS 1.3 could be so much simpler if they just removed any algorithm choices.