You're still not getting it....Minato was able to separate Sasuke from the Susanoo do to the Ribcage Susanoo being broken.
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Edit: Unlike Madara's Ribcage Susanoo...both Sasuke and Itachi Ribcage Susanoo front is enemy, but they can also put extra bones to put front as defense....this allowed for Minato to use the Chakra arms to separate Sasuke from the Ribcage Susanoo do to Sasuke not using that extra bones as front defense ....i can agree to some extend that he can only separate Sasuke or Itachi from the Ribcage Susanoo and that's if they don't put the extra bones i mention....... i'm not even sure about this since Sasuke ribcage Susanoo was broken and that's all....the other Susanoo have front defense that won't even allow for Minato's chakra arms to touch them.
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I even find hard for Minato to do this....since Sasuke also shows to create extra bones as front defense.