Great work. I learned of this very issue when the bug-report people combined this post with this one: Unable to attach screenshot images in macOS 14.0 when Wikilinks turned off (urlencode (U+202F) char)
And, yes, it appears to be some kind of “half-space” charater (U+202F，or   ) instead of the space character between the time and ‘AM/PM’. This prevents the file from attaching to Obsidian. Remove that character and the file can be imported correctly. That’s why my workaround above works, 'cuz it sidesteps creation of that weird character that was recently introduced by Apple.
My workaround (from above): I tweaked (in terminal) my screenshots so they default to jpg instead of PNG; I also tweaked MacOS preferences to use military time instead of U.S AM/PM. So, basically changed the default screenshot format to get rid of the ‘PM’. Problems go away.