[tialaramex]

As those release notes mention (and the new ones do too) you don't get a TLS 1.3 API

So you only benefit from features that already existed in TLS 1.2 (using the same API) or do not require an API such as the reduced round trips for initiating a new connection.

In particular you can't use 0RTT "Early" data because the specification asks that only be supplied via a dedicated API in both clients and servers.

The reason is that Early data might be replayed by an attacker in some cases despite all practical countermeasures and so your application software needs to make an explicit decision about whether it's acceptable to use Early data. Providing a separate API forces you to actually confront that decision and not get surprised by upgrading to TLS 1.3 and finding now you're subject to a replay attack.