The shinigami did not earn their bankais back in any way, shape, or form. They were taken from them with zero effort, they were totally beaten without them, and now because Urahara showed up out of nowhere literally through a magic door with a handful of magic beans, they all get their bankais back. There was no arc, there was no suffering, there was no effort. It is a solution with no struggle. Urahara in this instance literally is the god from the machine. He appeared during the climax and just fixed everything for everyone with the push of a button.
Also, regarding this "technique being used twice," you are writing fanfiction. Urahara did not explain in any capacity the specific mechanic behind how this pill is absorbed, nor the way they were teleported to people. You are guessing at why they work, deciding your guess is canon, and using that to fuel arguments.
I am all for defending things against silly attacks. This is not one of those times. Maybe next week it'll all make sense, but right now, much of this is gibberish and/or just lazy.