Find Results Inconsistent/Incomplete with Script Column

I am doing some testing involving identifying images with metadata in specific fields.

In this case I am working with a Script Column XMP Subject.

Using Find Files always finds fewer than if I sort by the XMP Subject column.

Might 'Find Files' be 'timing out' (I'm not sure that's the correct term), and thinking it's done enough or waited long enough for results, and so stops?

The difference in results is usually between 5% and 8%, and If I re-do find, results might include a few more or a few less files.

More likely to be an issue with the script (or tool it depends on), or the files being locked by something.

Thank you.