Soooo I have the exact same issue, and i only noticed it after i replaced my clutch & master/slave cylinder because of the dreaded csc failure... maybe it was there before and i never noticed it until now? im not sure. Another video on this
"First rev is with the clutch pedal out, second is with the pedal pressed in"
https://www.youtube.com/watch?v=ne6V8WQ_0Pg
The guy who posted that video said
"turns out it was the input shaft. had to get the transmission replaced" ... Not sure if it really ended up being that or not but worth a post
i wish i could contribute more but i'll be following this thread for sure in case you figure it out