[whpalmer4]

I bet this is the key:

From the release notes for 3.10.3

The location of clippings, templates, export plug-ins, and the default location for temporary audio recording files has moved into ~/Library/Application Support/The Omni Group/OmniOutliner. Your existing files will be copied to the new location the first time this version is launched.

You had already launched 3.10.3, so the new location had already been populated. The old location isn't removed when that happens, leaving it behind as a trap for the unwary...