Boruto: Naruto Next Generations' original manga version of the Mujina Bandits arc is one of the shortest in the series overall, and if it were going to be adapted directly it's afight that would probably only last for a couple of episodes. Conjecture suspects that the staff for the anime decided the same and ended up crafting an original prologue for this arc featuring the newish setting of the Hozuki Castle shinobi prison in order to better amplify the threat of the MujinaGang as they were really a much smaller crew in the manga.