I have done about 75 coding interviews for big tech companies. I have told a fair number of people (around 10) that I would be submitting a no-hire, but then I went on to coach them for another 15 minutes on how they could improve. I never once heard from anyone on the subject and all the people I told were actually grateful 1) that they wouldn't be left wondering and 2) how they could pass the next one.
I'd want someone to do the same.