Floyd Mayweather beating down some women, but couldn't KO them. They must have been some tough sparring partners. Floyd Mayweather having a hard time putting away a part-time security guard. Paul Spadafora treating Floyd Mayweather like his ho.
If Evander and Ollie were sparring G-Man, it's because they wanted to work on speed. That's why heavyweights spar smaller guys. G-Man was unsuitable for this kind of sparring because of his power and scrappiness.
I would add to this that there are many instances of one guy whipping and dominating another in sparring, and then when the two meet for a real fight, the situation is reversed: the sparring "loser" wins the real thing. I also know of instances in which world champs were having big trouble with novice pros, and threw them out of training camp for that reason. The "A" fighter doesn't need to get shown up in sparring: that defeats the purpose of training. There are "gym fighters" who look like God in sparring, but consistently underperform in real fights. There are other guys who tend to suck in sparring, but who consistently look great in real fights. You are correct that these legendary sparring stories don't necessarily reflect the truth about fighters' abilities.
I believe Bugner. I know that in 1969 or early 1970 his manager Andy Green brought him to the U.S. to pick up some seasoning sparring with the best. Bugner was only 19 years old at the time, but he was pretty big for that era (6'4", over 210 lbs) and was already pegged as the UK's star, up-and-coming heavyweight. During that tour, Bugner definitely sparred with Muhammad Ali, who was glad to get some pay (Ali was banned from boxing at the time). I don't find it surprising that Bugner would have gone a few rounds with Liston, too. In situations like these, the manager of the young prospect usually arranges for the world-level fighter to take it easy.
Here's a story of Tubbs getting tooled and dropped by Volodymyr, also talks about Peter who was one of the sparring partners This content is protected This content is protected :deal BJ made Jirov's legs wobble/buckle he didnt drop him and Jirov was out of the sport and had no punch resistance at that point. BJ posted the video to brag about it like the ****** he is. Guy got outboxed by Danny Green for christ sake enough said. That was Timur Ibragimov the journeyman, not Sultan.
Golota/Tua story This content is protected This content is protected This content is protected This content is protected
I think that was the open sparring they did on Miami Beach, Ali apparently beat Johannson for fun and made him look stupid, it was called off in a couple of rounds.