This shouldn’t be too much of a surprise, as TLS 1.3 has been out for many years and is widely adopted.
I haven’t paid too much attention to the TLS WG lately (for obvious reasons if you look at their mailing list), but I assume this is mostly a “if you want Post-Quantum cryptography, you need 1.3”.
I assume this is in contest with RFC10015 which proposes "Deprecating Obsolete Key Exchange Methods in TLS 1.2 and DTLS 1.2"[1]. Both are Proposed Standards submitted in July, by the same author. HN discussion[2]
TLS is an extensible protocol. For instance, you can add new key establishment algorithms or cipher suites. What this specification is saying is that the IETF will not be publishing such extensions for TLS 1.2. For example, they will not be adding post-quantum key establishment.
I haven’t paid too much attention to the TLS WG lately (for obvious reasons if you look at their mailing list), but I assume this is mostly a “if you want Post-Quantum cryptography, you need 1.3”.
[1]https://www.rfc-editor.org/rfc/rfc10015.html
[2]https://news.ycombinator.com/item?id=49139711
I thought the 1.2 spec was the frozen spec.
If you're going to add or remove features, follow semver and bump that number.