CCC Forum

This optional extension for Windows 10 might prove useful. So far as I am aware, Raw files include a small JPEG thumbnail which is used to display the shot on the camera's rear LCD. Presumably, this is what the Microsoft software does as well. Otherwise decoding Raw files could result in a significant performance hit and thumbnails would be slow to display.

https://petapixel.com/2019/06/04/micros ... indows-10/