Nope, it's definitely possible to pull duplicates before owning them all in every treasure from seal to summon, which is why I'm scared to go for my third rare in Kage treasure. xD
Yeah I pulled Chojuro at 60 then like an hour ago pulled Mei at 120, so its safe to say I am done with kage treasure because I got the 2 I wanted the most. Still need to get Sage Naruto though. I am kinda of afraid though I already got Orochimaru Traitor, but I think I need another 10-20 pulls before my next rare gonna gamble for Sage Naruto though since he is still a great ninja. I hope Sailor Sakura is in the next event cycle so I c*e her instead of Ao with Water main, Mei, and Chojuro.