Ahh, I think I see. So refreshing the album will remove the mtime from the database for all images in that album, but the 2nd phase will look for ANY images that have been updated more recently than the database, which will include all images in the current album, and *may* include other images also, but only if those images have indeed been changed since their last update.
I think I understand now. Is there a particular design reason for this approach, rather than specifically processing only the selected album? I will look through the code to see about making this affect only the selected album, but if there's a known particular reason this approach wasn't taken, it might be good for me to be aware of that in advance...