I can find a lot of Windows guidance and advice type sites but nothing on a Microsoft site that addresses the OP's heading "What is a moment update".
-Why is Microsoft delivering Moment updates?
-What type of updates can a user expect in a Moment?
-How often will they occur?
-Is a moment a preview release that will later be incorporated into a roll-up?
-etc
I know some of the answers via 3rd party sites but they tend to cherry pick and re-write. There is nothing that is as accurate as the official advice. If the information exists in a Microsoft blog, I ran out of patience before finding it.
EDIT: There is no mention of 'moment' in update terminology
The nearest would be 'feature pack'.
OP in my experience, it is not good practice for 'normal users' to manually install any update via settings, windows update that requires you to click a button. Be patient. New features will roll out at a later date. By then other 'real world' testers are likely to have uncovered any bugs (as happened with this months KB5022913 - some 3rd party utilities clashed with the the changed code: https://www.techgoing.com/microsoft-says-tools-like-startallback-are-incompatible-with-the-kb5022913-update/