I don't see this documented anywhere, and to me it's a bug.
If I have a TIFF (or JPG I guess) in Lightroom, and do an EDIT IN photoshop, using original, the image will be updated, but that image will not be marked for republish in any publishing collections in which it exists.
Lightroom should check to see if the image has changed and mark it so. I realize there are some timing and synchronization issues, but the current process (which leaves it always unmarked) means published collections are falling out of date.
Note it "notices" that a new preview is needed, so it should be able to also notice that "hey, and if I need a new preview and it's published, must need to republish also".
I've tried this with a couple of plugins, so I assume it is systemic and not plugin specific, but have not looked at the mechanics in the SDK. Am I correct this should be handled generally, not in the plugin?