Milestone and Release Candidate releases are unstable/testing releases and don't go through all of the requirements of a formal release.
Typically a Milestone or Release Candidate release is seen when working with other projects that are pushing through some kind of issue they are having.
The conversation on Milestone / Release Candidate releases are often seen on other issue tracking systems (like spring, conscrypt, cometd, eclipse ide, etc).
The formal releases enter a staging process, a period of testing, soliciting feedback in numerous forms (irc, mailing lists, issue tracker, gitter, stackoverflow, etc).
A major version release goes through a release review at Eclipse legal.
Any new dependencies go through approval at Eclipse legal.
The promotion to release occurs when the feedback warrants it.
A formal release announcement is made on jetty-announce mailing list.
After that, all of the followup work occurs (eclipse p2 repositories, documentation promotion, rolling older releases to archive status on download.eclipse.org
, etc ...)