BTW, a bit more comment on my previous one. When I added some new subdirs from PC to same root folder on sd card (with diff folder names, files in them), they happily showed up in the grid few, along with 4 new preview icons made correctly from the new folders! It would be a cool choice (like ‘enhanced grid view’) if it could be toggled off.
I was sad to hear you can’t dupe the behavior on your end.