Sparring 3 people all at the same time or other crazy methods

I remember a guy in my boxing gym who was so good that the coach threw 3 of us to box him.
I also recall Roy Jones being told by his father to only spar guys with only one hand.
Are methods like this needed to become successful? After all boxing is a ferocious sport and the training may as well be the same.

Sparring a number of guys at once was a method used a lot in the past.
Good for evasiveness and movement.

Sparring with just the jab is not uncommon for beginers.

Sparring should never be "ferocious," its meant to be a thinking and practicing exercise, thats the idea of these little games.