Hi,
Quickly implementing is fine. It's all relative though, as "quickly" can mean either a couple of weeks or a day (this depends on the complexity really). I previously used the phrase Just In Time, which describes the concept perhaps better.
I once again agree that it needs some time to gather feedback from users (community), but that was exactly what I was saying before ;) The feedback process can be facilitated by using the time tested milestone approach. For instance, for EE Security, we introduced the concept of an identity store using an API issue. This was then implemented in Soteria, and various milestones of Soteria were published to gather (community) feedback. Based on that feedback, the identity store feature was tweaked later on. So that's I think a good example of real-world user feedback, and code (product) first ;)
We basically followed the exact same process in JSF and Mojarra as well. All API issues were immediately implemented in Mojarra, and Mojarra published regular milestones which users used to play with (there even was at least one user who used those in production, something we didn't recommend, but the user did so anyway ;)).
As mentioned, the Jakarta EE spec process is still being worked on (I participate in this process as mentioned earlier), and once it's final we can really say something about it here, but in comparison, the JCP had several mandatory review moments during the spec cycle as well.
So eventually it's a combination between committer agreement, community feedback based on milestones, and likely one or more official review moments.
Kind regards,
Arjan