That’s impressive with headgear. It’s a shame he was a psycho, to this day I believe he would have cleared out everything in his way upto 140 including Pacman. Maybe not the most technically gifted but everyone in that time period at those weights was there to be hit, and with Valero it would only take one shot
Amateur headgear is made to make it harder to get a KO. (Causing less damage from headbutts is secondary) It causes more long term damage due to no KO though, so they were made optional for male competitions.
The amateur headgear with “open face” will not prevent getting KO’d, it will only (somewhat) help if you punch on the headgear. Headgear is mainly to prevent cuts from headbutts and protect your head from falling. Pro headgear that protects the face more (especially with the nose protection) will prevent a KO more and in sparring you use bigger gloves so it’s even harder to connect to bare face.
According to Boxrec, based on % KO from their wins Jose Lardued - 37% Arslanbek Makhmudov - 34% Hrgovic - 30% Saveliy Sadoma - 25% Beterbiev 25% David Morrell - 24% Jalolov - 23% Richard Torrez Jr- 22%
The description here claims that Jeremy Williams' amateur record was 304-5 with a 75% KO ratio yet other places it says 168-4 This content is protected
Unless you are in a high weight class, so upwards middle weight, stoppages or Ko‘s rarely happen and are often rather a result of beeing to skilled for your opponent. Ko‘s cause of sheer punching power, speed or perfect timing are actually super rare in amateur boxing. If amateur clubs would be very selective about pairing fighter, ko rates would be probably at less then 5 precent.
https://thegruelingtruth.com/boxing/japanese-lightweight-hopeful-shuchiro-yoshino/ Yoshino Shuichiro had 55 KOs in 104 wins and 124 fights.