Well, regardless of original precedent, it makes sense for captains to not have bankai yet just on account that most of the people with bankai should have been fighting and dying before so there wouldn't be an abundance of ones with bankai left anyway. Regardless of precedent, unless they wanted to have a very small number of divisions or pointlessly postpone the recreation of the Gotei 13, that precedent wouldn't matter.
Anyone who doesn't know that Ea is an anti-world noble phantasm is probably a person who has only watched the first FSN and nothing else or wasn't paying attention.
Tensa, I think that most forbidden kido would be actually lost unless someone dug up the nonexistent scrolls or there was a survivor who knew them. They are things to be taught, not so much a natural progression like bankai.