I've seen both videos before and they're excellent explainers on clutch type LSDs and the OS Giken design! Key thing with the OS diffs is using their special gear oil even though they do qualify a few alternative oils.

On a side note, the guy at the workbench in the second video who is giving us the rundown looks like he is about to burst out into laughter at any moment. I feel like someone behind the camera is doing their best to do the silliest things imaginable in an effort to get him to lose his concentration