AshSLR The team should just use an up-to-date Quest 3 if they care to check.
The issue with the 10-bit preview mp4s in the apps is the same as in some desktop browsers: they will not start playing when hovering the controller pointer over the thumbnail. If I remember correctly, in DeoVR the static picture remains while in Hyper it is replaced by an empty black thumbnail. No need to screen-record a video.
This is an example that has a 10-bit mp4 thumbnail: https://www.sexlikereal.com/scenes/slr-harem-maximum-bliss-84343
I think there is already enough information in this thread to understand what's causing this.