Yellow line indicator on left side of modern list items?

Hi

I have found that the yellow bar can also show if you have a content type with mandatory fields, that do not appear in the view, regardless of whether they have data, for example switching to the "Files that need attention" view doesn't show anything but normal views have the yellow bar beside items.

Unfortunately, I cannot seem to find any references to whether this is a bug or expected behaviour. Any ideas?

Paul Bullock