Block "Update Time" Sorting Rule

I’m looking for help sorting out block sorting rules…

We can use the standard “ASSET | Main Index | Dynamic Section & Children” block for the example here, but it applies to all asset blocks equally.

The problem we’re trying to fix is that when we update an existing article asset and check the “This update is important” box it doesn’t float the story to the top of the block. It remains buried under articles with more recent Start Times.

We should be able to fix this with the block sorting rules but have run into a wrinkle. It seems like a bug to me, but might be intended behavior.

The current sorting of our blocks is as follows:
Start date (descending)
Display priority (highest first)
Start date/time (newest first)

What I assumed would get the behavior we are after is:
Update time (newest first)
Start date/time (newest first)
Display priority (highest first)

However it appears that the “Update time” being referenced in the sort logic is the internal “Last modify time” and not the public “Updated:” time. This means that if we fix a small typo in a story it would bump the article to the top of the list even though nothing of substance was really changed.

The fix would appear to be making the “Update time” sort rule reference the “This update is important” checkbox and public display time whenever a site has the “Manually declare important updates” option enabled. The current behavior would be fine for sites without the “Manually declare important updates” option since then every internal edit results a change in the Updated: time displayed on the public site.

We basically want our block sorting to be based on the public “Posted: Wednesday, April 22, 2015 8:13 pm | Updated: 10:09 am, Thu Apr 23, 2015” text that readers see displayed on an asset.

Please let me know if I need to elaborate more or explain in more detail.