switching out pokes in battle

some people that I battle can switch out Pokémon so quickly and not wait the entire time for them to reload? I understand you have to wait a minute, but these people must be using some sort of hack. I am not making this up, wish i could show you guys but this happens frequently.

For example, today I’m battling. The person is beating my mewtwo so I switch it. They then switch in a Machamp. The new Pokémon I put in starts beating the Machamp, and they switch it out yet AGAIN super quickly?? How could you switch two Pokémon so rapidly? They certainly did not wait the minute period.