You do raise a good point and is something that we'll certainly be addressing more in the future.
3.5 includes various bugfixes and rollups as part of our monthly maintenance release cycle, as well as various backend enhancements. So whilst there are no specific features per-se in 3.5 over 3.4.1, there certainly are very valid reasons to upgrade.
All known bugfixes and addressed issues are all documented on the 3.5 Release Notes on Infosight under the "Resolved Issues" section (pages 13 - 20), so we do make a good effort to detail what the fixes are, and why people should consider upgrading.
Also bear in mind that the notice that is received for 3.5 is sent to various customers on lesser firmware revisions as part of the automated white-glove treatment Infosight provides. They might not necessarily be on 22.214.171.124 as you are, so the features offered in 3.x are still valid to point out as a one-document-to-serve-them-all requirement.
The release note format has been updated to include a new New Features in x.x.x.x section. The release notes for 126.96.36.199 include this new section (there are no new features in the release). I believe this addresses your request. Going forward, all release notes will use this format.
I also added a document with links to the 3.x release notes.
I've noticed that the NimbleOS release notes do a poor job of calling out the specific features added by a given release of NimbleOS; I am currently running 3.4.1, but the 3.5 release notes read like release notes for the entire 3.x series of software, not specific to the 3.5 release.
To wit, here's the header for the new features section:
Recent Release Features
The following new features are available in 3.x releases:
Please consider either a callout that lists the specific enhancements added by the last few versions (along with the version in which each was added), or maybe supply a complete list of version-specific enhancements in each discrete version's release notes, in addition to the essay-length "new to 3.x" section.