Well re-reading the chapter, Toshiro's and Byakuya's plan was pretty stupid, that's how Gerald grew to such a giant size in the first place; he got smashed with senbonzakura.
I dunno, this whole thing with Yachiru is weird. I mean Yachiru exists in a physical form, she has her own zanpakuto and even a cool shikai to go with it. But given what we probably don't know, she could be like some form of an Asauchi I guess? It's sorta like what Starrk and Lilynette had I guess, in Lilynette being Starrk's resureccion, though in their case they were originally 1 hollow that split itself into two, but also explains why Starrk didn't have a normal sword.