OneDrive can do some strange things with previews and thumbnails, as a result of some files being offline and the previews/thumbnails for them being generated by a completely separate system running completely different software which runs in the cloud. (Otherwise, switching to thumbnails mode would either not work for offline files or cause all of the files to be downloaded locally, which is something Microsoft have aimed to avoid with newer OneDrive vesions.)
Some 3rd party components may also treat OneDrive folders differently, e.g. to avoid pulling down all of the offline files if you switch to thumbnails mode.
As you said in your other thread about this, you see the same thing in File Explorer, so this is nothing to do with Directory Opus or the version of Opus in use. The things that the thread above talks about were differences between Opus and Explorer (due to the OneDrive web service apparently being limited to 255x255 thumbnails), which we worked around. If you see the same thing in Opus and Explorer, it's unrelated to this thread.