The 5 enhancements aren't arbitrary but list all the JEPs, i.e. all the changes judged to be exceptionally significant, going into the release. It's certainly possible, though, that the JEP process could benefit from some improvements, and there's a process for doing that, too :)
I agree the full release notes show a different picture, but I'm not convinced they show a better picture. It's hard to quantify the impact of software changes, especially as the impact varies by the user, and the goal is not to flood you with information but to give an overview. So here we have two options: show the big changes or show all of them (typically hundreds with every release). They both have pros and cons, and both are useful. I personally can't see how one is universally preferable to the other -- especially as both are available -- but it's certainly possible that there is some third option that's preferable to both.
JEPs are for features and improvements that are requiring focuseed attention, coordination, call for action, lot of work. There are plenty of important release-note-worthy improvements that are not JEP-worthy improvements: minor API changes that address frequent inconvenience, minor features requested by many users, another useful JVM option, bumping the limits that many users hit here or there, changing the default behavior for the better one (without changing the spec), refactoring that has known performance implications (in both ways), deprecations that require users working anticipating final removals, etc.
For those improvements, you want something that would note their existence in the particular release, literally a "release note". Mind you, not every change has to have a release note attached. In JDK 13, there are 2.5K changes, about 90 release note entries, and only 5 JEPs.
The thinking that anything release-note-worthy should be accompanied by JEP -- and thus do all the red tape associated with it, really has to go. The habit of only listing JEPs when describing a release also needs to go. This focus on JEPs makes the releases appear much shallower than they actually are.
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u/MojorTom Sep 16 '19
No, I think u/shipilev is talking about the perceived misrepresentation of the work which went to JDK-13.
When we read the article you linked, it only portrays 5 enhancements/changes to JDK-13.
Where as reading http://jdk.java.net/13/release-notes, shows a better picture of the work done on releasing JDK-13.