I think that might have been Blu where he ran one of the legs in Super league with no shoes at all.
Edit: Norwegians - #2 by fruit_thief
But I still agree with the general point. I have gone sockless in sprint and oly, but wore specific tri shoes for that which were designed to be softer inside for that reason (asics noosa tri). I’ve always worn socks in 70.3 and up. Even when trying to qualify for 70.3 worlds (where I think it came down to a handful of seconds).
I think the likelihood is the pros do it because those seconds matter. And it probably is true that someone like Blu is training it weekly if not more. If you watch his insta he was always doing brick sessions going straight into reps off the bike in no socks. So it’s likely there is a skin conditioning aspect.