App Store on High Sierra suggests Mojave-only updates I'm currently on macOS High Sierra (10.13.6) and I've just received three update notifications from the Mac App Store:


Keynote 8.2 update
Numbers 5.2 update, and
Pages 7.2 update


All of them are marked with Requires macOS Mojave and iOS 12 note - and when I try to Update any of them or all at once, nothing happens (I've tried to reboot the OS already). I want to stick to macOS High Sierra for now, and as far as I know, macOS High Sierra 10.13.6 will be supported for quite a long period of time, same as all previous macOS versions in the past.

Do these macOS Mojave only updates suggest that any further iWork office suite updates will support only the latest, upcoming macOS Mojave? How about security and other bug fixes then? What if one wants to stick to macOS High Sierra until its end-of-life but keep all their apps (including iWork) up-to-date (at least when it comes to bug fixes, not necessarily new features)?

Is is possible to mark these updates as ignored, but still receive any bug-fixing updates e.g. for Numbers 5.1? Does Apple even support its office suite for anything but their newest OS version?
The current latest version of the three iWork apps (as mentioned in the question), are supported on macOS High Sierra 10.13 and iOS 11. You are right, that the apps as well as the OS will be well supported into the future.

1. Pages

 



2. Keynote

 



3. Numbers

 



However, as mentioned in the release notes for the apps, certain features require the app to be running on macOS Mojave and Siri shortcuts requires iOS 12 which is the first iOS version to support this feature.


Pages for macOS
What's new in Version 7.2



  Support for Continuity Camera allows you to take a photo or scan a document with your iPhone and have it automatically appear in your document on your Mac. Requires macOS Mojave and iOS 12.



Pages for iOS
What's new in Version 4.2


  Support for Siri Shortcuts. Requires iOS 12.





Keynote for macOS
What's new in Version 8.2



  Support for Continuity Camera allows you to take a photo or scan a document with your iPhone and have it automatically appear in your presentation on your Mac. Requires macOS Mojave and iOS 12.



Keynote for iOS
What's new in Version 4.2


  Support for Siri Shortcuts. Requires iOS 12.





Numbers for macOS
What's new in Version 5.2



  Support for Continuity Camera allows you to take a photo or scan a document with your iPhone and have it automatically appear in your spreadsheet on your Mac. Requires macOS Mojave and iOS 12.



Numbers for iOS
What's new in Version 4.2


  Support for Siri Shortcuts. Requires iOS 12.