As far as I’ve noticed, major SUs come with release notes, but I’ve had several minor updates over the last couple of months with no notes at all, just a button that takes you to a “Thank you for being with us” type of announcement.
I like to know what I’m getting; just something like “Performance and stability improvements” would at least be something.
Wouldn’t you?
Almost always, release notes for updates are posted in News & Announcements. I suggest marking that category as “Watching” so you always get notified of something new 
Can the release notes be directly readable in the updater screen, with a link to a web page with them, consistently, every time?
Remember only a tiny fraction of MSFS simmers use this forum and will ever see something posted here.
First place I look. Never found anything.
This was the last known update to MSFS, unless of course you are in the beta.
City Updates & World updates typically pose a mandatory update to the sim. 
But I do agree, it should also include the release notes inside the simulator. Added my vote!