Looks like a lot of faffing about in that video link, job done 2 mins tops inc polish.
Agree theres some anomallies, second cut file to diamond paste i think not along with no quick cooling.
Anyone thats ever done by this similar means will know the heat carries on rising in the part after heat is removed no matter how slow the build up is.
Used to do long items many years ago, thats hard screws are easy. If overdo it just repolish and heat again, good enough for £6 figure value items on show.
Supposedly you can cool by using parafin, have tried but didnt seem any better.
To get a translucent colour in stainlesses is really trial and error, at best a brown/purple.
Theres also chemical blacking hot or cold and the old heated oil as mentioned in above post.