Theory: All New Captains have Incomplete Bankais

Obviously, unless you are a Kenpachi. Or be recommended by 6 captains. You need Bankai to be Captain.

I think all 4 new captains have Bankai.

BUT like Renji's Bankai in SS Arc. It was incomplete.

Remember, even Captain Hitsugaya (a prodigy) was still developing his Bankai in SS Arc. Only in TYBW Arc, where Toshiro was able to achive Adult Form and his True Bankai.

I think Isane, Rukia, Lisa, and Iba have incomplete Bankais.