Different sets of whistles to use on sheepdogs

why do we work sheepdogs on different sets of verbal commands or different sets of whistles? The only reason i put different commands or whistles on my dogs is so that i can work them together doing a sheep job. the different whistles mean that i can control each dog separately if you like this video and would like to see more explainer or training videos, then please take a look at the churchmount sheepdogs Patreon account the different whistles that i use on my working sheepdogs, are the ones i use for their sides (their left and right hand)