I didn't see the video, but I suspect there is a temp where the light goes on, and you were at that temp...and then dropped below it enough that it went off...just like you thought.
Glad you're good, but keep a close eye on coolant level anyway.
Upcoming NYC dates: Jan 8 and 27. See Facebook for other shows and PM me if you can make one...love to see you there!
Mangofy your E46!